Google Business Account Recovery

I need expert help regaining access to my Google Business. Somewhere along the line I changed the primary sign-in email, and now I can’t even remember what that new address is, which makes the standard Google recovery flow a dead end.

Here is what I know and have already tried:
• I completed Google’s account-recovery form several times, supplying every date, password and phone number I could remember. No luck so far.
• I still have my usual laptop and phone that were used to sign in before the change, so device-based verification is an option.