How to sync your Photos App in iOS 18
In certain situations, your photos on your iOS devices don’t sync automatically, such as when being on a cellular connection or being on Low Power Mode.
In iOS 17, it was really easy to resume sync by simply tapping Sync Now at the end of your Camera Roll.
In iOS 18, there is no Sync Now button at the end of your Camera Roll. You have to click on your iCloud account in the top right corner, and then hit the Sync Now button there.
Took me forever to find this setting.