Hi fellow pilots! I am posting here a fix to a linking problem, maybe someone also got stuck there. I was looking for a fix to my issue all over the net but none of the existing posts was helpful. I had an upgrade notification few days ago (since I don't connect my iPad to wifi too often). I've connected iPad to P4 and tried upgrading the firmware. Unfortunately the operation got stuck at 99% and after ca 5 hours P4's battery died. As I couldn't reconnect drone to iPad or controller I have decided to re do the upgrade with the Assistant 2 app. Unfortunately even though it said "update successful" I was not able to re-link the controller with the bird. Controller was working with iPad but could not see P4. P4 was starting up normally then blinking yellow tail LEDs. important: what was strange, was the fact that the linking button on the P4 (the led above SD slot) was blinking red when there was no SD card and was solid green when there was SD card. The working fix, as suggested by DJI support (mail support was the one to give the fix, chat support was my first bad experience with DJI): Please try to relink the drone using the app without the SD card inserted on the drone. If you are still unable to link the drone and the remote, please uninstall the DJI assistant 2, then reformat the SD card of the drone, restart the iMAC before installing the DJI Assistant 2. Once done, please try to reupdate the firmware of the drone, restart the drone, then relink it while the SD card is on the aircraft. It is not super clear, but I have put the formatted SD card into P4 before connecting to the computer and making an update. Hope it works for you too!