I’ve got the PAP3 (MAG) here and it works nicely with PMDG 737. I have A/T mapped to a switch on my X56 HOTAS and if I wish to disengage A/T I use that, and the MAG switch disengages just fine. I’m using SimAppPro 1.16.60 btw.
But if I try the same method on 777 300, it’s not working. Interestingly if I use the VC switch to disable A/T it works, and also trips the MAG switch off.
I’m puzzled, and it would be nice to flip the A/T off as I can with 737 by using a physical control.
Any tips appreciated 
EDIT… I am aware that (as far as I know) a 777 will touchdown with A/T still engaged, but it then retards and finally auto disengages, though the pair of physical switches stay in the “On” position with the pushbutton control only ceasing to be illuminated (i.e. deactivated). If I’ve something to learn there I’m all ears so this is really trying to understand if the PAP3 MAG is capable of clicking “Off” when a keybind is used. I suspect the 777 A/T systems are more complex than 737 tbh!