Trying to add domain to mail account gives error

Trying to add domain to mail account gives error

I'm trying to add the domain "shiningconcept.co.uk" to my mail account, but I keep getting the following error:

The email address you have entered belongs to a different deployment/region. Please contact support@zohoaccounts.com for assistance.

This may be happening because, when I first tried to set up my mail account using the domain name, the page froze, so I re-did the setup. Perhaps the domain name is now linked to some limbo account?

Any help would be greatly appreciated.