iPhone is stuck while syncing Photos to iCloud

is it trying or just paused... what does it say at the bottom of your iPhone photos library in the "Recents" album, if you scroll all the way to the bottom it will say how many photos and videos, and something about the cloud sync status, either that it is sync'd, or some reason why it stopped like optimizing battery or optimizing performance and you can click to resume the sync. And check wifi if you have Cellular turned off for Photos in system settings.