Just subscribed to lightroom mobile and it only syncs small catalogues (approx. 300 images). My larger catalogues (2 to 3,000 images) don't sync. No error messages. It just doesn't show up and the images show "pending" when you put your cursor on the sync icon of each image.
Very frustrating as I thought this was the solution to my back-log of editing.
Noel
www.cohartphotography.com