Missing photos

Hi, using Lightroom CC on my Android tablet and some photos that I have previously imported, edited and published have gone missing. I have 31 pics from 2nd June ok, but there are a large number I took on the same shoot that are no longer available, even though I had edited and published them using the tablet. The same thing has happened with the next 2 weeks worth of picture (several hundred taken during a recent trip to Portugal) which once again I have imported, edited and published. All of these should have been backed up to the cloud, but they're not showing up either on the tablet, or using the desktop versions.

The next set of pics I have available are from 14th June and it seems to be working as normal again.