I opened a tech support case and was able to get this working by setting up a second port channel.
I'm working on an HA project, but can't get the interfaces to negotiate. 2 x PA-3220 v8.1     2 x Dell N4032F switches latest recommended firmware The firewalls are setup for active/passive HA and the switches are configured for MLAG and have a LAG setup to connect to the firewalls. The PA ae interface on the active firewall shows one physical interface as active, but the other is 'not active (negotiation failed)' resulting in an amber link state. I've checked all of the settings on both the PA and switches and it looks like it should be working. What logs and settings should I check again?
LAG to Firewalls won't Negotiate