Recently Samsung had discontinued the Samsung Gallery sync and have replaced it with OneDrive sync.
This has caused many problems for everyone. One issue, in particular, is that the sync has stopped working and people can't figure out how to fix it. The instructions below are what I did to fix the issue.
This fixed the issue for me and I hope it will for you too!
I finally solved it by cancelling sync with Samsung gallery/account and resetting the OneDrive settings to sync.
All works as it should now.
Sadly I have had to do this COUNTLESS times because somehow it just "magically" keeps shutting off, so in my opinion this is NOT a fix at all, a temporary patch at best in my desperate attempt to preserve my photos. Now if the developers could figure out how to make it STOP doing that, THEN it would be considered a fix to a small part of a much larger/more complicated disaster.