Hello everyone, I registered an account just to tell you what I have done, after I had the same error today. As someone earlier said, the world has to be generated with Biomes o plenty. So what I did, after some research, I added this to my server.properties: level-type=BIOMESOP After this the world generation worked without a problem. Just make sure, that you replace level-type if already there, or change just the value. Also you might need to delete older worlds, if they're having the same name. Hope this helps some of you!