It’s really finicky right now. I actually swapped my GPU out because I couldn’t get it to work on my AMD card. Put my 2080 back in and it’s working now. Make sure you try building/rebuilding the landscape nanite mesh.
One big key thing to take note of is that in the material, you don’t do anything to the displacement mask->displacement input of the material. Any modifications other than a straight pin from one to the other and it messes everything up it seems. For instance, it breaks the center position really badly and you’ll be floating like 30 units off the ground.
The only way you can adjust the effect is in the material details panel(deselect all nodes)->displacement->Magnitude. It’s kind of annoying because if you’re making a master material, to then create instances off of for various different layers, you can’t individually adjust their displacement amounts without breaking the whole thing. I imagine the whole system will go through quite a few more iterations before it’s production ready.
EDIT: Oh and I’ve heard that some people can fix the vanishing mesh issue by adding some trivial amount to the displacement amount in the material. Like going from 0.25 to 0.25001, so it’s probably some caching issue that you have to force a rebuild on by adding the tiny amount.