Could you please send me a LR Desktop diagnostig log - best as a private message with a downloadable dropbox link.
You can trigger the log via LR Desktop preferences -> Lightroom Mobile and when you hold down the alt key you will notice a generate diagnostic log button.
In addition could you give some more infos what you are seeing. What is the Sync-Status within Lightroom desktop? Pending Photos? Are you able to sync new photos (or changes) from the Mobile app to Desktop but not the other way around?