Could be a LOT of things.
Fist - are you using billboards at a distance? If so, are the billboards even visible when overhead?
Second - Are you forcing LODs when capturing?
Third - It seems that currently the latest engine version is bugged.
For me - the instances aren’t showing up at all IF they pop up within the shadow of another tree. to be precise it’s not even the shadow. I think it’s the radius value being set in the brush or something similar to that.
The foliage checkbox in the Advanced Show Flags definitely works - it does enable/disable and render/not render the foliage that works. The problem is that Not all foliage works.
I think maybe Simple Collision has something to do with it. A mesh with it doesn’t render for me, whereas another without renders. up to a point at least. Clicking several instances of it seems to make them all not render.
Then again, if I add 7 instances of the same foliage to the same part that’s being captured they all seem to disappear, so perhaps the Actor Instancing for the foliage is functioning incorrectly in .24
I think this needs a bug report - just not sure what to do in order to give them something reproducible…