I have 2 PCs which I want to connect to a L2TP/IPSec VPN, one of them runs Ubuntu 16.04 and it works fine. The other one runs 18.04 and it can't connect to the server, although the settings are exactly the same. I compared every detail in the settings between the two computers. I even exported the settings on the working one and imported them on the other one, but it still doesn't work. On a Windows computer and on my Android phone it is also working.
So I'm wondering what's the difference between the VPN software on 16.04 and 18.04. Can anyone help me with that?
I already tried installing Libreswan, stopping xl2tpd and deleting the secrets file as suggested on these pages, but my problem still persists: