Hi Amberschild,
Welcome to the Apple Community.
Apple support have an article online (link below) to help you.
You might want to check your settings,
and see that everything is set up so iCloud can work smoothly.
Set up and use iCloud Photos
Eg: Your photos and videos are stored in iCloud in their original formats at full resolution.
This includes HEIF, JPEG, RAW, PNG, GIF, TIFF, HEVC, and MP4,
as well as special formats you capture with your iPhone or iPad, like slo-mo, time-lapse, 4K videos, and Live Photos.
https://support.apple.com/en-us/HT204264
If you need more info:
More articles follow.
Set up and use iCloud Photos on all your devices
https://support.apple.com/en-au/guide/icloud/mm7e90c1ba48/1.0/icloud/1.0
Upload and download photos and videos using iCloud.com
https://support.apple.com/en-au/guide/icloud/mmb5dbaf376f/1.0/icloud/1.0
How iCloud Drive works
https://support.apple.com/en-au/guide/icloud/mm19ef899373/icloud
Use iCloud Drive on iCloud.com on your iPhone
https://support.apple.com/en-au/guide/icloud-iphone/mmd0b4a7f5e8/icloud
Set up and use iCloud Drive on all your devices
https://support.apple.com/en-au/guide/icloud/mm203b05aec8/icloud
Still more info:
iCloud Support
https://support.apple.com/icloud
Hope this helps you :)