Do you use more than 1 browser at the same time? If yes: Figure out when it works and when it does not. I had the issue that even though Bitwarden worked fine with each of these browsers (let’s call them: browser1 and browser2) if only one of them was running. It turned out that starting browser1 and then browser2 was ok for both, but first starting browser2 first and then browser1 caused browser1 not to support that shortcut anymore.
Something else that can cause issues is important for owners of an AMD graphics card if the Radeon Software is installed as it already occupies that shortcut. To deactivate this start the Radeon Software, go to Hotkeys, look for Performance Hotkeys and remove the shortcut for Toggle Performance Logging:
And finally: Check if any other software you have installed already uses this shortcut.