Cannot paint on object or on masks

I opened your file (it updated to the current version on opening) and had no problems painting on the paint layer or the masks. Note the mask builders make that paint effect hard to see on the masks so try adding an 'Add Paint' filter within the mask for easy painting.

Dave

Hello Cyril, thank you for reaching out. 

Here is the .spp file.

Hello @reabudi,

It's a bit hard to troubleshoot without more info. Could share a video of the issue, or even the .SPP file?

Let me know.