Today, I received emails from Firebase that my projects changed from a paid to a free plan due to an issue with my billing account. (And no, payment was not the issue. I do not have any outstanding payments. That was the first thing I checked.)

When I log into GC, the top bar in red shows: Your account has been closed. You can no longer access Google Cloud. Contact support for further assistance.

My billing page shows: This billing account is closed. Reopen it to continue using linked projects. But when I try to reopen it, it says: You can't reopen this billing account because this account is not in good standing.

The payment overview page says: Your payments profile is currently suspended because some information on your account couldn't be verified.

Pointing me to this URL: https://support.google.com/pay/contact/account_verification

So apparently, Google needed to verify something about me, and instead of asking for it, they thought, why not close the account first? What's the harm in that?