Trouble Painting and Using Masks on My Custom Mesh in Substance Painter

Hi everyone,

I'm new to Substance Painter and I'm having trouble with my custom mesh. I can apply materials like roughness and metallic just fine, but I can't paint directly on the mesh or use masks — nothing shows up when I try.

I’ve checked the UVs and they seem correct (everything is in the 1001 tile, no UDIMs). I also made sure to disable automatic unwrapping when creating the project. The mesh loads correctly, and I can see it in the viewport, but painting just doesn’t work.

I’ve tried using paint layers, different brushes, and switching view modes (Material, Base Color, etc.), but still no luck. Everything works perfectly when I use the default mesh (Meet Mat), so I’m really confused.

Could this be a shader issue or something with the texture sets? Any help would be greatly appreciated!

Thanks in advance