No sound from headphone or internal speaker

I have an iPad 4th gen, there is no sound from the internal speaker, nor from the headphone jack. I've swapped all parts in the ipad and another motherboard works, but this one is obviously stuck in some mode I can't really explain. When I volume up or down while on the home screen, it shows volume up and down fine, but I think it should show ringer up and down. I plugged in headphones, and unplugged them, and it gets stuck thinking headphones are plugged in, but there is no sound from the headphones. Youtube videos do not play, they appear to start playing but they ultimately just sit there and never play. Itunes store sample music does not play either. I click on the song I want to play a sample of and the play/pause effect of the sample graphic flashes and nothing happens, like I never hit play. I've tried airplay to my apple tv, and when I select apple tv from the bottom swipe up menu, it goes right back to the ipad, it will not try to air play. This is a very strange situation and I'd like any help I can get. I've reset all settings, upgraded ios to the latest, cleaned out the headphone port, swapped the main headphone/camera/mic/volume button cables with working ones, I've changed the internal speaker with a working speaker...I'm stuck.