Collision detection on landscape is off , help please

So i am studying unreal for some time now , with some tutorials i made simple building system that spawns part of the building by matching collision boxes.

It worked till i started doing it on the landscape instead of static mesh floor.

The issue is that on floor it easily connects and shows possibility to build withing my set range (lights green)

But when i start to do it on the landscape it rarely giving me constant “connection” to the surface and set turn green to red ( cant build in that area)

i am attaching a video to show the issue , so maybe there is a box that i should tick in landscape to make it work as smooth as with floor? or maybe there could be another issue

english is not my main language , sorry for possible mistakes