@jannex: I host that server for this guy kiliandu95
You can try to contact him for help and try with the creator of the original tibia script. Also it would help if you posted the logs of a failed join attempt here. (Start new game, try to join, open console and copy/paste content).
What would definitely help is to reset the server, but that would mean your level will also be 0 again :S
Edit: I can't join anymore now either ;). Got the exact same problem as you and probably a lot more people since almost noone is playing anymore!