Assuming that you are signed in (as 'something' is making it to the Cloud) are these RAW photos? As some users are reporting issues...
Here are some links from the LR Mobile Forum with possibly the same issue:
Are the photos in a Collection as previous advice from Akash at Adobe has been "Try creating a new collection and add the same set of images and see if they Sync up"
Seems like there maybe some kind of intermittent bug if Collections aren't used.
You may have to get one of the Techs to have a look, try one of the Mobile forums:
This has more Adobe employee interaction: