Follow mode, video file reports unknown error

Could someone please assist. I am new to litchi and have a DGI mini2.
When I first used the app, follow mode video playback worked perfectly. Now for some reason I get the report unknown error, yet on all the other modes, playing back video works well? " Your advice would be greatly appreciated."

You proberly turned the drone off without first stop recording.
Put the sd card back in the drone, then turn the drone on and off. This might fix the corrupt video file.

Or you could try this software to fix corrupted video files:

Thanks for the feedback, I reset the app, formatted the SD card and it seems to be working . Much appreciated!!