I'm getting this error today out of nowhere. Everything has been working normally and today it just randomly started doing this. Passwords are correct in Allmon.ini and manager.conf. I can't find any logs as it says, so I'm not sure where to look. Everything else works so if there's no solution it will just stay broken. This is a raspberry pi 3 with the latest version of ASL3.
Did you check the server logs as prompted? journalctl -u allmon3.service.