Could you please try to remove the sync.lrdata file and restart Lightroom.
This would restart/refresh the sync (metadata only).
You can find the sync.lrdata file here:
On Mac it's at /Users//Library/Caches/Adobe/Lightroom/Sync Data/Sync.lrdata
On Win it would be at C:\Users\\AppData\Local\Adobe\Lightroom\Caches\Sync Data\Sync.lrdata
Let me know if this helps.