Is it a common problem for iPad Air 2 microphone to not work? My method of communication is dictation, so the microphone is critical. It works on my synced iPhone 6.
Backup the iPhone and then restore to factory. Then as you set up the iPhone restore the backup.
If the issue persists. Restore again and then dont restore the backup, set up the phone as is. If it works then your files have corrupted the audio. If it doesnt work, then it needs to be repaired. Take it to the Apple Store for repairs.
My iPad Pro's microphone recently stopped working almost completely – "almost" because you could still recognise loud sounds in a recording, but it was effectively unusable. The "Hey Siri" setup process wouldn't work etc.
The cause turned out to be mechanical: there was dirt stuck in the tiny microphone hole. I carefully dug it out with a needle and the microphone returned to its original performance.
The microphone's location depends on your iPad model. On my 9 inch Pro, it's a tiny (almost invisible) hole exactly in the middle of the top frame (the one with the power button).