I have looked at a few threads on this and none help me. I think this issue could be different. I have an existing terrain block, that is landscaped. On this block I can not use the paint terrain tool, however I can use all the other options like erosion, raise or lower terrain, etc. Now when I add another terrain block, everything works, without changing anything, so surely it cant be Any ideas? Edit: Before I posted this, I found solution, so posting for others that have the same problem: It was one of: Removing all layers, adding them back again Replacing layer.