LR "Still syncing with Lightroom Mobile" - How do i fix this

[katiegm]

About a month ago, when i was shutting down LR on my Mac, i got this message

I tried waiting for a while but nothing happened. I get this message every time i shut down now.  I do not get a parallel message when i shut down LR Mobile.  I cannot figure out what picture they are talking about and i cannot figure out how to get it to finish syncing.  Everything seems to sync just fine between LR and Lightroom Mobile.  But i worry that there is some image someplace that is stuck.

Does anyone have any ideas how i can clear this up?

Thanks so much

Katie Moran