Had you save the logs in cloud before the update? I had to delete my app and when I reinstalled it, all my videos, photos and logs were gone. I was able to retrieve the logs from the cloud but the vids and pictures are gone.
In case it's of use to anyone else, I lost my flights when I deleted my DJI Go app trying to get the controller to connect to the aircraft after the latest firmware update.
I had never uploaded to the DJI cloud. So thought it was all lost forever.
However I had a backup of my iPhone form a while ago that would have had all the logs.
So I did a fresh backup go my IPhone. Restored it to the older version that had the logs.
Synced to the DJI cloud.
Then restored again to the just created a few moments ago backup of the iPhone.
Voila. Phone as it was plus the flight logs retrieved.