I updated my photoshop thinking 22.4.2 would fix my "select and mask" problem but NO, anyone else having a problem on Catalina? I select subject or any manual selection (doesn't matter how I select) and then try to use the "select and mask" button and the right rail flashes the panel with all the adjustments in it and then just disappears so I can't do anything???
If you invoke Select and Mask any other way, does it work? (e.g., Select > Select and Mask on the menu bar)
If you disable your GPU, does it work? (Photoshop > Preferences > Performance > Graphics Processor Settings > uncheck Use Graphics Processor. Restart. Select and Mask will be dog slow but this is a good way to find out if your GPU's driver has gone kablooey.)
Neither of these suggestions work. I'm having the same problem. When clicking the Select and Mask button or in the menu, I see the window flash on my screen for a split second and then it's gone. Select and Mask is broken on 22.4.2 for sure.