I have for years used same M-Audio midi controller with both Cakewalk and Gig Performer. (on Windows 10 and 11)
Today…
if I open Cakewalk first, the midi device works in Cakewalk, but not in Gig Performer.
if I open Gig Performer first, the midi device works in Gig Performer, but not in Cakewalk.
Again, it has worked for years (in live shows) using same M-Audio midi controller simultaneously in both programs (Cakewalk and Gig Performer).
More info: I tested, and can use, M-Audio Oxygen 61 (3rd gen) in both programs (Cakewalk and GigPerformer) simultaneously.
But same test with M-Audio 61 MKV fails to work in both programs (Cakewalk and GigPerformer) simultaneously.
Clue: M-Audio had drivers for the older Oxygen 61 (3rd gen) and I use those drivers, but M-Audio says they offer no drivers for MKV, because it uses Windows system midi drivers.
That must be why… BUT I WAS USING THE MKV with both programs for the past two weeks since I purchased the MKV. I think maybe a recent Windows update is on the brainstorm list of why it stopped working.
I completely disabled Windows updates because I don’t have time to troubleshoot what Microsoft screwed up in their updates. I personally have very bad experience with Windows Updates.
I ended up installing feature upgrades twice a year (of course, I make full system backups).
It sounds like the Windows MIDI driver, which is not multiclient, is used from now for any MS reason. I forgot about the process, but there is a way, when you connect a USB device, to force Windows to assign it a specific driver. In your case it should be your M-Audio drive if it is still supported by Windows, which could be why it is not assigned anymore to your M-Audio keyboard controllers. If this doesn’t work you will have to find a workaround using virtual MIDI ports. 