Can you give some computer specifications? Also try deleting the world in /Zomboid/Sandbox/servertest and see what happens. Anything from the console with the server will help also (Client also possibly, really depends.) Shivian will give you the specifics he's the server owner. I guess he doesn't want to post, he says that he deleted the servertest and has checked the server logs and there are no errors. According the logs the server is running fine. He's also tried deleting world.db, didn't work.