For some reason snap is not working in my piano roll view on midi. It seems to work fine in some projects and on the main timeline, but not on PRV. Grrrr. am I forgetting something. It's set to "measure" and smart grid is turned off.

The snap has a separate PRV that can be turned on. It's controls are toward the top right of the PRV window in the title bar area.

Having said that the global should work there as well. Check you intensity settings Prefs-->Customisation--->Snap to grid. If that's on light that can sometimes give the impression it's not working.