Per your material,
Whatever is painted with ForestFloor should receive the grass - without any modifications microtexturing etc.
Setup wise, your instancing is a mess. Fix it/revise it.
Could be the issue if your camera is further than the cull distance.
Another option vould simply be the grass mesh LOD settings or lackthereof.
Or the material of the grass if it does special things like move the grass under the labdscape based on distance.