old iphone photos not syncing to icloud
I recently purchased an icloud storage upgrade, so i was trying to backup all my photos to icloud, but when i do this, only the most recent 2021-2022 photos and videos have uploaded to icloud. All my photos from 2016-2020 won't sync into icloud and upload. i checked all my settings are correct and the phone was connected to wifi and a power source. what other options can i try to upload these photos?
iPhone 13 Pro