If you have run out of iCloud storage, you can take one of two approaches you can take to obtain more available iCloud storage so you can resume syncing:
- Free up old or unused data in iCloud so give you more available storage within your existing iCloud storage allotment.
- Purchase additional iCloud storage from Apple.
NOTE: If you have reached the iCloud storage limit for an inventory shared with you by someone else, that inventory is stored in their iCloud account. The owner of the iCloud account will have to either remove unwanted iCloud data to free up more space or purchase additional iCloud storage from Apple in order for you to continue syncing data to the inventory they have shared with you.
Freeing Up Unused iCloud Data
To learn how to remove unused iCloud data, refer to this article from Apple on managing iCloud storage: Manage Your iCloud Storage
Purchasing Additional iCloud Storage
To learn how to purchase additional iCloud storage from Apple, refer to this article from Apple Support: Upgrade to iCloud+
If you have an Apple One, plan you can purchase more iCloud storage using the link above or upgrade your current Apple One plan to a plan that includes more storage: Change Your Subscription From Apple