Photos no longer uploading to iCloud because “iCloud Storage is Full” when it actually isn’t

If your iCloud storage is full -- Manage your iCloud storage - Apple Support.

If your device's storage is full, here's how to check -- How to check the storage on your iPhone, iPad, and iPod touch - Apple Support & About storage on your device and in iCloud - Apple Support.

AndyTheGreat876 wrote:

If you are asking about my iCloud, it’s only around 100mb. It seems like most of my photos are now saved on my device storage because of this problem.

No. I am asking about your device storage. Go to Settings > iPad Storage. Look for Photos. That is how much space that Photos would need to backup to iCloud.

You have to have enough space to backup all of your photos. How much storage is being taken by Photos on your device?

That's just Photos. Other data could push it over.