Have you narrowed down whether it’s a problem with the shortcut or a bigger problem with the command or the file?
If the shortcut does not work but choosing File > File Info works, then the problem is with the shortcut. Check your Mac for any background processes (like utility software that was installed) that might have taken over that shortcut. Also, open macOS System Preferences, go to the Keyboard panel, click the Shortcuts tab, and make sure that keyboard shortcut combination is not also listed for another application which may be overriding Photoshop.
If neither the shortcut nor the command works, there may be a problem with Photoshop. If you restart Photoshop and it still happens, you might try resetting Photoshop preferences or reinstalling Photoshop.
If File > File Info do not work when you try to edit the metadata in Photoshop or Adobe Bridge, or in any other software that can edit metadata, then the problem is with that document, such as possible data corruption.
Those are not all the possibilities, but they are examples of how you can use troubleshooting techniques to narrow down the real cause.