After updating from OTRS 5 to Znuny 6.0.36 LTS, the login button is greyed out and we can no longer sign in. Also the login screen seems to have an incorrect layout. Normally it's a centered square on the screen, however now the login is screenwide size.

I followed the manual for upgrading: https://doc.otrs.com/doc/manual/admin/6 ... ating.html
I have also found this topic: viewtopic.php?t=39826
With the help of this topic I was able to make the button no longer greyed out, however pressing the button does nothing.
Any help towards resolving this issue will be greatly appreciated.