Paint foliage on imported static mesh not working but 'fill' does work

Hi,

I’m trying to paint foliage on an imported static mesh in 4.15. The paint foliage will not work on the static mesh but the ‘fill’ command works fine. I usually generate landscapes topologies in other software and import those meshes into unreal, so would like to know the best method to paint and add foliage too these imported meshes.

Cheers,

James