user100704: My log was stuck on this for 30 minutes:
2019-12-09T22:33:17Z txindex is enabled at height 0
2019-12-09T22:33:17Z txindex thread exit
2019-12-09T22:33:17Z Bound to [::]:8333
2019-12-09T22:33:17Z Bound to 0.0.0.0:8333
2019-12-09T22:33:17Z init message: Loading P2P addresses...
2019-12-09T22:33:17Z Loaded 587 addresses from peers.dat  3ms
2019-12-09T22:33:17Z init message: Starting network threads...
2019-12-09T22:33:17Z net thread start
2019-12-09T22:33:17Z dnsseed thread start
2019-12-09T22:33:17Z addcon thread start
2019-12-09T22:33:17Z init message: Done loading
2019-12-09T22:33:17Z opencon thread start
2019-12-09T22:33:17Z msghand thread start
2019-12-09T22:33:28Z Loading addresses from DNS seed seed.btc.petertodd.org
2019-12-09T22:33:28Z Loading addresses from DNS seed seed.bitcoinstats.com
2019-12-09T22:33:28Z Loading addresses from DNS seed dnsseed.emzy.de
2019-12-09T22:33:39Z Loading addresses from DNS seed seed.bitcoin.sprovoost.nl
2019-12-09T22:33:39Z Loading addresses from DNS seed     seed.bitcoin.jonasschnelli.ch
2019-12-09T22:33:39Z Loading addresses from DNS seed dnsseed.bitcoin.dashjr.org
2019-12-09T22:33:50Z Loading addresses from DNS seed dnsseed.bluematt.me
2019-12-09T22:33:50Z Loading addresses from DNS seed seed.bitcoin.sipa.be
2019-12-09T22:33:50Z 282 addresses found from DNS seeds
2019-12-09T22:33:50Z dnsseed thread exit

And then after 30 minutes, showed this:
2019-12-09T23:05:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 1890 seconds ago)
2019-12-09T23:16:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 2520 seconds ago)
2019-12-09T23:26:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 3150 seconds ago)
2019-12-09T23:37:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 3780 seconds ago)
2019-12-09T23:47:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 4410 seconds ago)
2019-12-09T23:58:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 5040 seconds ago)
2019-12-10T00:08:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 5670 seconds ago)
2019-12-10T00:19:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 6300 seconds ago)
2019-12-10T00:29:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 6930 seconds ago)
2019-12-10T00:40:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 7560 seconds ago)
2019-12-10T00:50:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 8190 seconds ago)
2019-12-10T01:01:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 8820 seconds ago)
2019-12-10T01:11:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 9450 seconds ago)
2019-12-10T01:22:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 10080 seconds ago)
2019-12-10T01:32:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 10710 seconds ago)
2019-12-10T01:43:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 11340 seconds ago)
2019-12-10T01:53:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 11970 seconds ago)
2019-12-10T02:04:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 12600 seconds ago)
2019-12-10T02:14:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 13230 seconds ago)
2019-12-10T02:25:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 13860 seconds ago)
2019-12-10T02:35:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 14490 seconds ago)
2019-12-10T02:46:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 15120 seconds ago)
2019-12-10T02:56:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 15750 seconds ago)
2019-12-10T03:07:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 16380 seconds ago)
2019-12-10T03:17:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 17010 seconds ago)
2019-12-10T03:28:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 17640 seconds ago)
2019-12-10T03:38:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 18270 seconds ago)
2019-12-10T03:49:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 18900 seconds ago)
2019-12-10T03:59:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 19530 seconds ago)
2019-12-10T04:10:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 20160 seconds ago)
2019-12-10T04:20:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 20790 seconds ago)
2019-12-10T04:31:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 21420 seconds ago)

Any ideas what could be wrong?
UPDATE
I've tried deleting the blocks and chainstate folders. Same thing happens. It gets up to here:
2019-12-10T04:53:34Z Loading addresses from DNS seed dnsseed.bitcoin.dashjr.org
2019-12-10T04:53:34Z Loading addresses from DNS seed seed.bitcoin.jonasschnelli.ch
2019-12-10T04:53:34Z Loading addresses from DNS seed     seed.bitcoin.sprovoost.nl
2019-12-10T04:53:46Z Loading addresses from DNS seed seed.bitcoinstats.com
2019-12-10T04:53:47Z Loading addresses from DNS seed dnsseed.emzy.de
2019-12-10T04:53:47Z Loading addresses from DNS seed seed.bitcoin.sipa.be
2019-12-10T04:54:00Z Loading addresses from DNS seed dnsseed.bluematt.me    
2019-12-10T04:54:00Z Loading addresses from DNS seed seed.btc.petertodd.org
2019-12-10T04:54:00Z 282 addresses found from DNS seeds
2019-12-10T04:54:00Z dnsseed thread exit

And then does nothing. I assume it's going to start with the "Potential stale tip detected" errors soon. 

user100704: This answered my question. 

put these lines to your conf file, shutdown and restart syncing again
addnode=104.237.131.138
addnode=151.80.205.132
addnode=192.155.82.123
addnode=74.220.255.190
addnode=80.100.203.151


And I had to unblock outgoing ports  8333.

100704: <p>My log was stuck on this for 30 minutes:</p>

<pre><code>2019-12-09T22:33:17Z txindex is enabled at height 0
2019-12-09T22:33:17Z txindex thread exit
2019-12-09T22:33:17Z Bound to [::]:8333
2019-12-09T22:33:17Z Bound to 0.0.0.0:8333
2019-12-09T22:33:17Z init message: Loading P2P addresses...
2019-12-09T22:33:17Z Loaded 587 addresses from peers.dat  3ms
2019-12-09T22:33:17Z init message: Starting network threads...
2019-12-09T22:33:17Z net thread start
2019-12-09T22:33:17Z dnsseed thread start
2019-12-09T22:33:17Z addcon thread start
2019-12-09T22:33:17Z init message: Done loading
2019-12-09T22:33:17Z opencon thread start
2019-12-09T22:33:17Z msghand thread start
2019-12-09T22:33:28Z Loading addresses from DNS seed seed.btc.petertodd.org
2019-12-09T22:33:28Z Loading addresses from DNS seed seed.bitcoinstats.com
2019-12-09T22:33:28Z Loading addresses from DNS seed dnsseed.emzy.de
2019-12-09T22:33:39Z Loading addresses from DNS seed seed.bitcoin.sprovoost.nl
2019-12-09T22:33:39Z Loading addresses from DNS seed     seed.bitcoin.jonasschnelli.ch
2019-12-09T22:33:39Z Loading addresses from DNS seed dnsseed.bitcoin.dashjr.org
2019-12-09T22:33:50Z Loading addresses from DNS seed dnsseed.bluematt.me
2019-12-09T22:33:50Z Loading addresses from DNS seed seed.bitcoin.sipa.be
2019-12-09T22:33:50Z 282 addresses found from DNS seeds
2019-12-09T22:33:50Z dnsseed thread exit
</code></pre>

<p>And then after 30 minutes, showed this:</p>

<pre><code>2019-12-09T23:05:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 1890 seconds ago)
2019-12-09T23:16:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 2520 seconds ago)
2019-12-09T23:26:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 3150 seconds ago)
2019-12-09T23:37:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 3780 seconds ago)
2019-12-09T23:47:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 4410 seconds ago)
2019-12-09T23:58:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 5040 seconds ago)
2019-12-10T00:08:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 5670 seconds ago)
2019-12-10T00:19:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 6300 seconds ago)
2019-12-10T00:29:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 6930 seconds ago)
2019-12-10T00:40:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 7560 seconds ago)
2019-12-10T00:50:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 8190 seconds ago)
2019-12-10T01:01:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 8820 seconds ago)
2019-12-10T01:11:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 9450 seconds ago)
2019-12-10T01:22:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 10080 seconds ago)
2019-12-10T01:32:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 10710 seconds ago)
2019-12-10T01:43:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 11340 seconds ago)
2019-12-10T01:53:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 11970 seconds ago)
2019-12-10T02:04:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 12600 seconds ago)
2019-12-10T02:14:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 13230 seconds ago)
2019-12-10T02:25:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 13860 seconds ago)
2019-12-10T02:35:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 14490 seconds ago)
2019-12-10T02:46:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 15120 seconds ago)
2019-12-10T02:56:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 15750 seconds ago)
2019-12-10T03:07:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 16380 seconds ago)
2019-12-10T03:17:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 17010 seconds ago)
2019-12-10T03:28:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 17640 seconds ago)
2019-12-10T03:38:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 18270 seconds ago)
2019-12-10T03:49:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 18900 seconds ago)
2019-12-10T03:59:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 19530 seconds ago)
2019-12-10T04:10:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 20160 seconds ago)
2019-12-10T04:20:32Z Potential stale tip detected, will try using extra outbound peer (last tip update: 20790 seconds ago)
2019-12-10T04:31:02Z Potential stale tip detected, will try using extra outbound peer (last tip update: 21420 seconds ago)
</code></pre>

<p>Any ideas what could be wrong?</p>

<p><strong>UPDATE</strong></p>

<p>I've tried deleting the blocks and chainstate folders. Same thing happens. It gets up to here:</p>

<pre><code>2019-12-10T04:53:34Z Loading addresses from DNS seed dnsseed.bitcoin.dashjr.org
2019-12-10T04:53:34Z Loading addresses from DNS seed seed.bitcoin.jonasschnelli.ch
2019-12-10T04:53:34Z Loading addresses from DNS seed     seed.bitcoin.sprovoost.nl
2019-12-10T04:53:46Z Loading addresses from DNS seed seed.bitcoinstats.com
2019-12-10T04:53:47Z Loading addresses from DNS seed dnsseed.emzy.de
2019-12-10T04:53:47Z Loading addresses from DNS seed seed.bitcoin.sipa.be
2019-12-10T04:54:00Z Loading addresses from DNS seed dnsseed.bluematt.me    
2019-12-10T04:54:00Z Loading addresses from DNS seed seed.btc.petertodd.org
2019-12-10T04:54:00Z 282 addresses found from DNS seeds
2019-12-10T04:54:00Z dnsseed thread exit
</code></pre>

<p>And then does nothing. I assume it's going to start with the "Potential stale tip detected" errors soon. </p>
 100704: <p><a href="https://bitcoin.stackexchange.com/questions/73607/testnet3-node-sync-process-is-very-slow">This</a> answered my question. </p>

<blockquote>
  <p>put these lines to your conf file, shutdown and restart syncing again</p>

<pre><code>addnode=104.237.131.138
addnode=151.80.205.132
addnode=192.155.82.123
addnode=74.220.255.190
addnode=80.100.203.151
</code></pre>
</blockquote>

<p>And I had to unblock outgoing ports  8333.</p>
