Hello @TomW860. Thanks for coming into the Community! I'm sorry that you are seeing this error when editing a contact. Our upper level of support is investigating what causes this blank error to appear. You can still update this contact by going to their contact profile and editing the address from this page. I apologize for any inconvenience this caused you!
FYI even though an error appeared and the email address didn't change on the screen I discovered it was changed in the contacts ....
Thanks for letting us know! I will pass this along to our upper level of support. We're glad to hear you were able to get the email address updated in your account.