I was able to re-connect my P3 by going to the app Clicking the "..." located on the top left corner, Click the "Remote Controller Settings" and clicking "Linking Remote Controller". This worked for my issue...hope it works for you as well.

I have exactly the same issue. I have updated the firmware to 1.9.2 and flew 30 minutes then landed OK (no crash). Moved 3 km away and wanted to fly again, no video signal at all, it was saying "strong interference" ... then "remote control signal week" ... i was able to still control the motors with the RC. The link led on the AC was grene on the RC red. It would not relink, tried multiple times. I have trtied SD firmware update and it always fails ...
[00014874]Version checking[1]...
[00014925][04 00][00] v1.51.0.0 -> v1.51.0.0
[00015047][11 00][00] v2.0.0.33 -> v1.8.0.0, firmware v2.0.0.33 not support.
[00015091][11 00][00] v2.0.0.33 -> v1.8.0.0
[00015250][11 01][00] v2.0.0.33 -> v2.0.0.33
[00015298][01 00][00] v1.14.4920 -> v1.14.4920
[00015348][01 01][00] v1.14.4920 -> v1.14.4920
[00015430][03 05][00] v34.2.0.9 -> v34.2.0.9
[00015523][03 06][00] v2.4.20.50 -> v2.4.20.50
[00028086][07 00][00] device not detected.
[00028176][09 00][00] v0.1.1.1 -> v0.1.1.1
[00028273][12 00][00] v5.9.0.0 -> v5.9.0.0
[00028387][12 01][00] v5.9.0.0 -> v5.9.0.0
[00028498][12 02][00] v5.9.0.0 -> v5.9.0.0
[00028606][12 03][00] v5.9.0.0 -> v5.9.0.0
[00028660]Packet upgrade failed at version checking.

Now the RC and AC are totally disconnected. Called DJi today they told me i would have to send it to repair but because it's more than 12 month i will have to pay for it. VERY DISAPPOINTING ... if it was not for the software update i was very happy with DJI was working perfectly until this ...

DJI - any solutions to all people who got their drone messed up by a software update ? What if we are outside of warranty when a SW broke the product ? ... why should we pay for this ?

Vlad
Montreal, Canada

You can reset the controller to factory defaults. With everything disconnected turned off. Turn on the remote  Turn the Gimbal dial all the way to the right(The manual reads right but I had to turn mine counter clockwise to the left to get it to work ) you then will toggle S2 back and forth 4 times you will hear a Beep. If you don’t hear beeps turn the Gimbal in the other direction all the way and repeat the process. If you hear a Beep. 1.        Your controller is Good 2.        You just reset the controller You can now re-link the drone to the controller.

Zediathewolf Posted at 2017-1-13 11:06
We are having the EXACT same problem. Only used a few times then lost camera signal (Not "No signal" but "Disconnected") Now the remote is not connecting to drone. I did try to link rc and drone with button but no use. Want to also try resetting before sending it back. VERY DISAPPOINTING...

You can reset the controller to factory defaults.
With everything disconnected turned off.
Turn on the remote
Turn the Gimbal dial all the way to the right(The manual reads right but I had to turn mine counter clockwise to the left to get it to work ) you then will toggle S2 back and forth 4 times you will hear a Beep. If you don’t hear beeps turn the Gimbal in the other direction all the way and repeat the process.
If you hear a Beep.
1.        Your controller is Good
2.        You just reset the controller
You can now relink the drone to the controller.

Holmeswake Posted at 2017-4-18 23:14
DJI-Jamie

The reason I say its a scam is that there is no way for me to know the real problem. DJI holds all of the cards. DJI has my drone, DJI wants my money in order to fix it and DJI will get my money so I can get my drone back. No communication just a $ amount i need to pay to get it fixed and returned.

I also had the same problem after a firmware update (P4P)  could not connect the controller to the bird, got on the phone with DJI followed there direction and still could not get them to connect, sent my bird and controller to DJI and it cost me $811.00 to get mine fixed had to replace controller and I can't get an answer as to what was wrong with the controller for it to be replaced, I've sent 3 message and no one has gotten back to me so I know ow you feel.

vladagri Posted at 2018-1-24 19:03
I have exactly the same issue. I have updated the firmware to 1.9.2 and flew 30 minutes then landed OK (no crash). Moved 3 km away and wanted to fly again, no video signal at all, it was saying "strong interference" ... then "remote control signal week" ... i was able to still control the motors with the RC. The link led on the AC was grene on the RC red. It would not relink, tried multiple times. I have trtied SD firmware update and it always fails ...
[00014874]Version checking[1]...
[00014925][04 00][00] v1.51.0.0 -> v1.51.0.0

Did you at any time use Magic Power?

I had the same issue. I found it was the Go app. I had to uninstall the go app and then reinstall.