Why do you use the term "backup email?"   Did the efile verification code not arrive in your regular email?   Also check your email's spam/junk folder to see if it somehow ended up there.

If you received a code, and it's not working, you have to remember to leave the original interface open that asks for the code.   Use a different tab, different window, different browser, or your phone to check your email.  If you close the original interface, the code will always be seen as invalid or expired.

You can try to verify your email address from inside your Intuit Account Settings or can change it there, if necessary.

• Log into Online TurboTax, then in the left menu column scroll way down to Intuit Account.
• Then once in the account choose tab Sign In & Security.
• See if your email address has a tiny link beside it that says "not verified".  If so, click that to verify.
• It may then send a link to your email instead of a code by which you can verify it.
• Perhaps once you verify it there by that method in the account settings, it won't ask you to verify it again when you are efiling.
• But if it does ask you again when efiling to enter a code, remember to leave the interface open while you retrieve the code from your email.

If after all that, you still can't resolve your issue, here's how to reach TurboTax Support 5AM-5PM Pacific, Mon-Fri.

FAQ: What is the TurboTax phone number?
https://ttlc.intuit.com/community/using-turbotax/help/what-is-the-turbotax-phone-number/00/25632

If you use Free Edition and don't have phone support, another way to reach them if you have social media is to direct message a Support agent:

https://x.com/TeamTurboTax

or
https://www.facebook.com/turbotax