This usually happens because you have changed the world generation name but not told the server what world to load. To resolve this just ensure that the following match in your server config file
world=C:\Pingperfect\Users\yourusername\serviceid#\Worlds\Pingperfect.wld
worldname=Pingperfect
Looking for a game server host known for brilliant 24/7 customer support and quality hardware?
Try a Pingperfect Terraria server today! https://pingperfect.com/gameservers/terraria-game-server-hosting-rental.php