I am in a similar situation, but in my case when I try as the primary admin to elevate a standard user to admin, I receive a prompt to verify my identity with a popup box headed "Let's make sure you're you".  The only option it offers is to call with a code.  I do not wish to use a telephone number to verify and don't know why I can't use the same email as I use to log into the account in the first place.  I have just spent an hour on a chat via the "Contact customer support" link on the popup box, and they insist on using pageviewer, which I was unable to make work the last time I had a problem.

Is there no way to work around this issue?  I am really getting tired of everyone demanding my telephone number for identification.