Keyboard shortcut for Hide/Show Frame Edges not working in InDesign 2023 Mac

It works for me in Monterey. A couple of things to check:

In InDesign, if the Default keyboard shortcut set is the one selected in Edit > Keyboard Shortcuts, then the current shortcut for Hide/Show Frame Edges should be Ctrl+Command+H. This is what it should say when you click the View > Extras submenu and look at the shortcut for Hide/Show Frame Edges. If the shortcut listed for that command is something else, then a customized shortcut set for InDesign is in use, so make sure that’s what you intended. And you can set it to the shortcut you want.

If it does say the shortcut is Ctrl+Command+H, well, that is working for me in InDesign in macOS 12 Monterey*. If it doesn’t work, macOS or another application or utility is overriding it, then I agree you have to track down what it is, as Bill Silbert described. The first place to look is in System Preferences, Keyboard settings, Shortcuts tab. Unfortunately, both macOS and InDesign do not provide any kind of search in their keyboard shortcut customizers, so you might have to page through all the shortcuts to find the conflict. If the conflict is not in macOS Keyboard settings, Shortcuts tab, look in any application or utility you might have installed that can assign system-wide shortcuts. For example, I use screen recording software that has shortcuts that can override other applications when it’s running.

*Note that you said you have “the latest system software” and then call it macOS 12 Monterey, but that is not the latest system software. Since fall 2022, the latest system software has been macOS 13 Ventura. If you are actually running Ventura, note for the previous paragraph that Apple changed the name of System Preferences so that it is now called System Settings.