I flew my Mavic Air the other day with no problem. I charged all my batteries to 100% and today went to fly. Controller fully charged. I could not connect drone to my controller. My djiGo4 opened and could not connect to my Air. I got a message that the quad was not on level ground and that I should shut down and start again. I shut down and restarted and, I still had same problem. I was using a mini4 and removed the iPad and put on my iPhone 11 which also would not connect and the controlled still did not connect. I then noticed that my iPad had connected with the drone and I was able to start the Air, but could not control it and "returned to home" and it came down and stopped. I flew my mini all morning with no problems. How do I find out if there is a problem with my controller for the air. I am apparently up to date with my app and as I said earlier in this note, the Air worked well a few days ago.