Synced collections appear in Lightroom Mobile as empty albums (no photos come through)

Hi! I'm desperate for help after upgrading my Lightroom and amongst several issues- lost my ability to sync to Mobile/Ipad.

I am on Lightroom 13.3 because I can't upgrade past 13.5 without upgrading my computer software which I don't want to do.  I have no sync errors showing, and when I sync a collection, the album appears on LrM but not the photos inside of it. So obviously in some way, it is connected, but for some reason the collection appears empty.  

I spent 2 hours on the phone with Adobe and they couldn't figure it out either. They tried creating a new catalog, and rebuilding sync data and neither worked. Photos edited on the Ipad update on LrC but not the other way around. 

Sync is the center of my workflow as I do culling and editing of all client galleries on the Ipad so would SO appreciate any guidance!