Landscape LODs broken in an existing map

Hello

Landscape LODs don’t seem to work in an existing map.
If I create a brand new landscape in a new map, I can see LODs changing/blending changing in wireframe mode.

As you can see below, the LOD coloration shows that its changing but I don’t see any difference in tessellation through wireframe.

Any ideas?
Any way to rebuild Landscape LODs?

Thanks