Even with Align to Normal toggled on and Align Max Angle all the way up I can’t get any foliage to paint along surfaces that aren’t perfectly flat.
Is there some setting I’m missing?
It looks aligned to me, what am I missing?..
I assume OP wants it to paint onto the walls?
Ah… 
Now I’m wondering about the wall normals. Maybe try putting on a cube…
I tried this myself and I had to set the “Align Max Angle” value to 0
Then below that, Set the “Ground Slope Angle” value to over 90… (91 will do)
Its worth mentioning that the “Align Max Angle” doesn’t determine if the foliage mesh will be placed or not. Just how much they should rotate away from 0,0,0 when trying to match the ground normal
Thanks! This helped. For some reason “Ground Slope Angle” being too high caused problems, and everything I found online seemed to imply I should turn up “Align Max Angle” so your explanation is pretty welcome. Setting it to 181 also did the trick for painting foliage on ceilings.
Awesome. Glad I could help!