I can’t see my iCloud photos on photos

Device or computer?

IOS

Are you signed into Settings/Your Name/iCloud using the same Apple ID you used when the photos were synced to iCloud, and is Photos syncing on?

Try Settings/Your Name/iCloud and slide off Photos syncing. Wait a few minutes and then slide syncing on. Allow time for syncing to occur. The photos sync is very, very slow and could take a couple of days or more.

Last resort - have you tried signing out of iCloud, restarting the device, and then sign back in?

OS

Are you signed into System Preferences/iCloud (Apple ID for Catalina) using the same Apple ID you used when the photos were synced to iCloud, and is Photos syncing on? In Photos Preferences/iCloud, is iCloud syncing turned on?

Try going to System Preferences/iCloud (Apple ID for Catalina) and stop syncing by unchecking the box. Wait a couple of minutes, then check syncing. Allow time for the sync to complete. The photos sync is very, very slow and could take a couple of days or more.

Last resort  - have you tried signing out of iCloud, restarting, and then sign back in?