Niagara skeletal mesh material filter sample region

I’m not successful in spawning particles on a part of a skeletal mesh using a Material Filter in the Sample Region. I am using the Sample Skeletal Mesh location module with the Sampling region setup but I am not able to spawn any particles. I tried using other spawning modules like Initialize Mesh Reproduction Sprite but it doesn’t work as well. What am I doing wrong?
I have no trouble using the Bone Filter but confused why Material Filter isn’t working.
The emitter is a CPUsim.

Anyone figure this out? I would love some help as well… I don’t know how to get this working.