Paste Settings from Previous - shortcut not working

In Mac LR6 and now LR 8.2, the Paste Previous shortcut (command-option-V) is no longer working. The menu command works, but not the shortcut. Very frustrating. All other shortcuts work. iMac 5K, now running Mojave, but same problem in Sierra. I get a soft beep after keying the shortcut, like a mis-key beep. Maybe some background app wants that key combination, but I can't imagine what. Any thoughts would be appreciated