For reasons like this, it is always advised never to install beta firmware versions unless you know exactly what you’re doing. A lot of times, beta firmware versions are riddled with bugs and may render your primary device useless. Apple has already released the public beta for its upcoming iOS 11 and even though it’s quite useable, it still has a few bugs here and there.
I’ve been running iOS 11 developer beta 2 and the most recent public beta for about two weeks now on my iPad Air 2 and there has been this annoying bug making things difficult. The device often refuses to charge with the dreaded “this accessory may not be supported” error message displaying on the screen.
Unless you’re having a different issue or using a damaged charger, this problem seem to be perculiar to just iPad Air 2 running iOS 11. It doesn’t matter if you’re using the original charger or an aftermarket charger, there seems to be just one fix to this.
From my observation, if the charger is already plugged into the mains and you try to insert the cable into Lightning port of your device, this is most likely to happen. A simple fix is that sure works is doing it the other way round.
1. Unplug the charger from the mains.
2. Insert the cable into the Lightning port.
3. Plug in the charger back into the mains.
That is the simple fix that has been working for me since. Of course, it’s almost certain this is going to be fixed before the final version of iOS 11 is released to the public. This beta version is meant for testing, feedback, and improvement.