My Edge Profiles Will Not Switch With The Function Buttons Any More

This is usually a configuration state rather than a hardware fault, and the giveaway is that everything else on the controller works perfectly.

On a DualSense Edge, profiles live on the controller but their assignment to the function button shortcuts is managed through the PS5. Each shortcut slot points at a stored profile. If that mapping is cleared, which happens after a controller firmware update, after a settings reset, or if the profiles were created on a different console, the function buttons still work electrically but have nothing to point at, so pressing them does nothing visible. That matches your description exactly, including the last active profile staying put.

The first thing to confirm is whether the function buttons themselves register at all, and your test gives you that. If the Fn press shows up as an input but no profile change follows, the buttons are fine and the assignment is the problem. If the Fn press does not register as an input either, that is a different and rarer fault in the button itself.

Assuming the buttons register, go into the PS5 controller settings, open the Edge profile settings, and reassign each profile to its shortcut slot. It is worth deleting and recreating one profile as a test if reassigning alone does not take, because a profile stored in a corrupted state will sometimes accept an assignment without applying.

Two other things that produce this. A controller firmware update that has not completed leaves profile handling in a half state, so check for and apply any pending update. And on PC, profile switching behaves differently: the Edge's profiles are configured through PlayStation's own PC support rather than through Windows, so if you have only been testing on PC, confirm on the PS5 before concluding anything.