Shortcut "Remove from presentation" not working

Hmm, it should be an easy one, but I can't figure it out. I'm working with a Mac. Max shortcuts work, including "Add to Presentation" (Shift + Cmd + P). When selecting an object already added to Presentation, the menu item "Remove from Presentation" is active, and works fine if I choose it in the Object menu. But the shortcut (Option + Cmd + P) has no effect. Any pointer? Does my Mac short-circuit it? Thanks!