I have used iCloud on my Mac to store my Desktop and Documents folders for years.

I have an extra terabyte of iCloud storage that I'm not using, so I'd like to let a family member use it.

I have enabled "Family" in System Settings, and invited the family member, who has accepted (there is an explicit message that "All plans can be shared with up to five family members").

But, the other person is still getting a warning that iCloud Drive is full at 5 GB.

Can anyone confirm that it is possible to share iCloud Storage between family members, and point me to what I might be doing wrong?

Is there some difference between iCloud and iCloud+ that might be at work?

My main computer just says iCloud in the settings, but the family members' computer says "Upgrade to iCloud+ for more storage".