Hello,
My spark came to 3 days, and yesterday finally get out to use it.
In the first few minutes everything OK, I was able to use all the functionality normally, with and without the RC. In the afternoon when I went flying, when I took off I noticed that my gimbal was not responding more to the RC commands, he does not know any more and he also does not go down, he seems to be off. I set the spark and made lateral movements that normally the gimbal stabilized, and even so he was not moving.
I tried restoring factory settings, downgrade, and nothing worked.
The commands by gestures is more difficult to use because the camera is only in a position to identify me, I do not know what to do someone already had the same problem?
The aircraft did not crash, and in the app shows the whole status as "normal" and there was no gimbal error message at all, it just stopped working.

Did the gimbal feel soft when you power on the drone? Could you please provide me with a video of the gimbal and the screenshot of the firmware info (drone and RC connected, go to DJI GO 4, General Settings, About)? Thank you.

The same here with my spark. Gimbal shows down. looked without power at the gimbal. I tryed to refresh the firmware without luck.

here is a video of the power on sequence. Gimbal has no reaction.
https://www.dropbox.com/s/3m1526d7dehuvyz/MOV_1647.mp4?dl=0