I have started using Ubuntu version 16.04 for a while. My problem occures every time I upgrade Ubuntu.  The vpn connection works perfectly fine after the installation of the operating system, but as I upgrade the system for one or two times, the VPN connection fails in successfully getting established.I tried changing to systemd as I thought it might solve the problem by doing what XModulo has described,but I gained no result. I do not understand the meaning of the tail -f /var/log/syslog output, so I bring it here:Jun 25 23:17:54 UbuntuBox pppd[11302]:   Child process /usr/sbin/pptp 80.84.49.136 --nolaunchpppd --loglevel 0 --logstring nm-pptp-service-11297 (pid 11305) terminated with signal 15  Jun 25 23:17:54 UbuntuBox NetworkManager[907]: Child process /usr/sbin/pptp 80.84.49.136 --nolaunchpppd --loglevel 0 --logstring nm-pptp-service-11297 (pid 11305) terminated with signal 15  Jun 25 23:17:54 UbuntuBox NetworkManager[907]: Modem hangup  Jun 25 23:17:54 UbuntuBox NetworkManager[907]: ** Message: nm-pptp-ppp-plugin: (nm_exit_notify): cleaning up  Jun 25 23:17:54 UbuntuBox pppd[11302]: Modem hangup  Jun 25 23:17:54 UbuntuBox pppd[11302]: Exit.  Jun 25 23:17:58 UbuntuBox kernel:   [16385.969103] [UFW AUDIT] IN= OUT=enp3s0   SRC=192.168.1.102   DST=8.8.8.8   LEN=67   TOS=0x00   PREC=0x00   TTL=64   ID=22994   DF   PROTO=UDP   SPT=52516   DPT=53   LEN=47   Jun 25 23:18:03 UbuntuBox ntpd[10810]:   error resolving pool 0.ubuntu.pool.ntp.org:   Temporary failure in name resolution (-3)    Jun 25 23:18:03 UbuntuBox kernel: [16391.621292] [UFW AUDIT] IN=enp3s0 OUT= MAC=ff:ff:ff:ff:ff:ff:c0:4a:00:d5:1a:65:08:00 SRC=192.168.1.1 DST=192.168.1.255 LEN=72 TOS=0x00 PREC=0x00 TTL=1 ID=56088 PROTO=UDP SPT=520 DPT=520 LEN=52   Jun 25 23:18:13 UbuntuBox kernel:   [16400.982470] [UFW ALLOW] IN= OUT=enp3s0   SRC=192.168.1.102   DST=8.8.8.8   LEN=67   TOS=0x00   PREC=0x00   TTL=64   ID=25387 DF PROTO=UDP   SPT=39308   DPT=53   LEN=47 Unfortunately I am very new to networking and have no clue about the reason modem hangs up or why the child process gets terminated. Would you guid me through some steps to help my system's vpn connections start getting connected and working? Thank you very much in advance.
VPN connection fails to connect after upgrading ubuntu 16.04
systemd;vpn