Done button grey when trying to downgrade iCloud storage
I have logged in to iCloud on my Mac via settings/iCloud.
I have logged in successfully and deleted any backups and data that would have taken the storage over the Free 5GB, and when I am in the downgrade options, I can see a blue tick on the downgrade to 5GB Free, but the done button is grey and disabled and I am unable to select it.
Any ideas how to rectify this and apply the 5GB free option?
iMac, OS X El Capitan (10.11.6), null