Lightroom on iPad, syncing does not start

I have imported 53 photos from my camera memory card to LR on iPad. Now I want these to appear on my other devices, iPhone and iMac. On iMac I have both cloudbased LR and LR Classic installed. Nothing happens. If I click on the cloud symbol on the iPad it says syncing is active but 53 photos are waiting. How do I get the sync to actually start?
The syncing has worked before but I have not used this method to add photos for about six months (uses this method when travelling).