dallas, if it were me I would connect MIDI out your PC/device and use a MIDI monitor tool, such as MIDI OX, to verify your theory.
then if you haven't already try a factory reset and test MIDI out again. If it's really not working I would open a ticket with DSI support.
But if AT works over MIDI out after a globals reset but you're still not hearing it, try update the OS if needed and reload the factory patches. and find one with strong AT modulation to test with. Have you played around with the keyboard tracking modes to see if the problem is better or worse in a particular mode?
If you have another MIDI keyboard with AT, you could also try controlling the P6 with the other keyboard to see if the P6 responds to AT then. That may not fix anything, but you would have more info for DSI support to assist you.
Have you tried toggling PRESET to off, putting the P6 into live panel mode? after a globals reset, being in panel mode is the most direct way to test anything.
:j