Can't change my email address

I need to change my email address to my gmail address so that I can interface to Google Home, but whenever I try to do so the Tesla Account website comes up with

and

yet the email address I am changing to is my own gmail address and so cannot already be in use in Tesla's database.

I get the same error if I try to change to another of my email addresses.
What is going on, and how do I get someone to fix the problem?
Thanks.