I have UR44 audio/MIDI interface and AG06 audio interface connected on my mac. (AG06 doesn't have MIDI capability but mysteriously is observed as MIDI device from the OS)
My mac runs macOS Monterey.

MIDIGetNumberOfSources returns 3, which makes sense because the OS adds IAC driver on top of the two devices I've listed above.
So the program loops over three MIDI sources to get their properties by MIDIObjectGetStringProperty.
And It returns proper values for AG06 and IAC driver, but it doesn't for UR44.
It just gives me null(=0).

As an experiment I forced the pulldown to show the index at which UR44 should have been displayed and tried selecting that , but it just didn't work.

I'm sure that UR44 is recognized by the OS because other MIDI app(namely Logic Pro X) can use it.

I also tried connecting other device(UM-ONE), which appeared on the pulldown, but the message from it couldn't be received.
I'm not sure if UM-ONE driver has any problems or it's the same issue with UR44.

I still haven't figured out many points. I'll check them one by one later.

• Does it happen only on UR44?
• When did it start happening? From Catalina or from Monterey?
• Will the device work if the info is obtained? Possibly not as far as seeing the result with UM-ONE...?