Lightroom mobile not syncing all photos

Hey, @lucy_5527. Welcome to the Lightroom Community. I'll help you figure this out. 

Try adding flags/ratings or small edits to the images that do not appear in the shared album and waiting for the sync to complete. 

If nothing changes after a while, log in to Lightroom Web (https://adobe.ly/3uv2zCA) on a desktop browser with your Lightroom Account and look for the Sync Issues category near the Deleted section on the left part of the screen. If there are any Sync issues, check the file name, apply minor edits or tags, and wait a while to check if the edits sync to the cloud. 

If this does not help, ensure you have a backup of these images; you can clear them out & also delete them from the deleted section. 

After this change, let Lightroom sync for a while & check if it returns to normal.

Thanks!