Niagara issue on 4.20.3

Hi,
We are currently developing in UE 4.20.3 and trying to implement some particle effects using the new Niagara particles system. I’m trying to emit from an actor in the scene but it seems like the StaticMesh “source” button doesn’t work. I’ve tested the same thing on 4.21.2 which works as expected but we would like to avoid a version upgrade at this time, so if anyone has a suggestion for a fix, that would be great!

Thanks alot!