Sync super slow and getting stuck

Hi, I used to use an old version of Lightroom and decided to update to Lightroom CC so I could edit photos on my phone and tablet as well as laptop. I installed Lightroom CC and it all works fine except for the sync.

Sync only does about five photos and then stops. I have left it on for over 24 hours and it only synced about 20 photos. When I close and restart lightroom it syncs about five photos again and then gets stuck. This is super annoying and I can't work out how to fix it. I looked at older solutions and they all say to delete the Sync.lrdata file, but that only works for lightroom classic. I don't believe lightroom CC has one. If it does I can't find it.

Any help would be much appreciated. At present the only option I can think of is to keep restarting lightroom every five minutes or so. But as I'm trying to sync 3,000 files that will take weeks.

It's probably worth me pointing out that my internet connection is very fast. I have uploaded over 100 gigs to onedrive in a few hours, while streaming HD films. So it's not my internet connection that's the problem.

Thanks,

Harry