Lightroom not syncing back

Hi, I regularly start an edit on Lightroom on my desktop, hit sync and will often catch up on the edit on my iPad out and about, in between meetings. However, a couple of times recently I've noticed when I go back to my desktop after editing on my iPad, I go to export the shoot and it's not 'synced back' the edits I made on my iPad. I've tried renewing the sync which despite taking a long time, worked once, but not since.

Any ideas, otherwise it kind makes the cloud aspect redundant.