I sent my drone in for a motor cap replacement and when they sent it back it no longer connects AT ALL! Why did they tinker with it, all it needed was a new motor cap. I manually upgraded the firmware to the latest version in every device. I have tried linking it both using DJI GO app and the controller itself. No dice. In wifi mode my phone can find the drone's wifi (after upgrading everything) but the app doesn't see it and the RC is stuck in 'connecting'. These were all the suggestions the support email gave to me. This has taken so much of my time at this point I just want to get it connected again so I can turn around and sell it. Is there a reliable firmware set I should downgrade all devices to? This is maddeningly frustrating, especially since it worked JUST FINE before I sent it in for a simple plastic cap repair.

go into the app with the drone on, go to remote settings and you will see linking remote, select it and press okay and on the AC open flap where the sd card goes and press the small black button with a tooth pick and your remote should connect.

are you sure they did not replace the drone entirely - if so you might have to 'register ' again.

Did you try to change a USB cable? Please link the RC again and see if both of the firmware are compatible with each other.