Why would Shift+Control+F4 be locked out as a keyboard shortcut for an action?

Basically, what the title says- Latest Illustrator on Windows 11. I have a large list of actions that I use daily, and I have them all assigned to the “F” keys along with combinations of the shift and control keys. I just made 3 new actions, and I have Shift+Control F2, F3, and F4 available as shortcuts. The problem is, Shift+Control+F4 is grayed out and there is nothing I have been able to do to unlock it. I don’t see anything else using it either. What can I do to get this working?