Here is some of the comments I collected on this from around the web. When I get my replacement drone I will try not update the firmware.
I can't vouch for any of these...yet.
1. Go to Settings - Apps - DJI GO 4 - Storage - Clear Data. Before doing that do not forget to sync all flights in DJI GO 4 to do not loose anything.
2. Swipe down to find "recent" apps, click that, and then force quit the DJI GO 4 app by swiping up. Click back into the camera view and it should work. This has worked for me every time I have encountered the problem. Seems to be a memory issue.
3. Swipe down and turn the wifi off on the
SC it doesn’t seem to happen nearly as often, but when I turn the wifi back on it starts being more consistent with the grey video at startup again.
4. Relinking you could do from quick settings - swipe from top of screen and click option Linking. After that click button on drone which is under cover opposite SD card cover.
5. For me it was working so far without issue with latest version. Only thing I have done differently is that I have linked aircraft via Aircraft management and added my AC with name to SRC.
6. Hi DH the resetting the data in the Go4 app seems to be working up to now, i have had a SD card in the
SC for 4 battery changes and not had a glitch yet , time will tell, cheers and thanks for the advice
7. From DJI: Upon checking the thread you posted here, most users reported the drone shows grey screen after switching on but it recovered after several reboots. Did you still have the same problem? If yes, we recommend to reset the camera settings and then reset the factory data in Setting to see if the issue persists.
8. I had same problem. Go into camera settings and reset the camera and it works fine now.
9. My
Mavic 2 pro, and
smart controller started this issues with the latest firmware update. The only way I can get the grey screen to go away, and have the video work, is to remove the SD card from the drone. Then, everything works fine. Flew a couple of times, and thought it was an anomaly.. I then put the sd card back into the drone, and boom, instant grey screen. Then power everything off, take the card out power everything back on, and it works. Seems, at least for me is that after the latest update I can't use an SD card in the drone..