iCloud Contacts web interface: This contact couldn't be created because of a server error
I have recently started getting this error message every time I attempt to add a contact via the iCloud Contacts web interface:
Couldn't create "[contact name]".
This contact couldn't be created because of a server error. Try again later.
When that happens, the new contact is nonetheless listed on the Contacts web interface. However, it fails to be synchronised to Contacts on my iPad, iPhone and Outlook on my PC.
This worked fine for me for years. I'm not aware of having made any changes at my end.