I havent flown in several weeks. My 3 batteries were at about 50% charge. I fully charged them. With neither one of them I can turn on the drone. I press the power button for a few seconds, see the 4 green LEDs and nothing happens.
The last time I used the Air, everything worked perfectly ok.
Any clues what could have happen?

It sounds like you are not switching the aircraft on the correct way. Press the power button briefly and release it, then press it again and hold it on until the four geen LEDs come on.

Geebax Posted at 5-29 14:48
It sounds like you are not switching the aircraft on the correct way. Press the power button briefly and release it, then press it again and hold it on until the four geen LEDs come on.

You are so right!. I had forgotten how to do it!
Thank you.

Hello there nywrecker. I am sorry to read and know that you are having issues in powering on your DJI Mavic Air before and it is great to know that you were able to power on your DJI Mavic Air by following the instructions given by Geebax on post #2. If you have any issues with DJI or with your DJI drone. Kindly please post it here at DJI Forum. Thank you and have a safe flight always.

It's embarrassing but the same thing happened to me over winter. I spent about 10 minutes trying to turn on the drone and all I was doing was showing the battery state.:-)

It happens.