A long time ago I set up a Gmail backup account and transferred all my Yahoo Mail emails there to save them for posterity. Once in a blue moon I would log in, reminisce over 20+ year old messages and attachments, and move on. I did just that in June 2021, except this time it triggered some suspicious activity flag and that account got locked. Unfortunately (lesson learned!) I did not associate any recovery information with this address, so Google basically refused to let me back in, despite the valid password. I tried every suggestion I came upon - resurrected old phones and laptops, attempted logging in in the same geographical area that I used to live in, etc - nothing worked. Eventually I came to terms with the idea that those memories are forever lost, behind Google's unresponsiveness.
Every few months I tried logging in, without any expectations or success. Except today it worked! Logged from an incognito window and during the recovery process got asked for a phone number. And then I was in (and as a first step fixed the backup info). I can't help but notice that almost exactly two years have passed since the lockout. Don't know if there is significance there, but just wanted to share with folks that there might still be some hope. Too many stories of locked out Google accounts with zero transparency or follow-up possibility from the company.