I had the literally the exact same thing happen to me about a month ago. The automated account recovery provided by Gmail was not helping the least bit, and I desperately needed to talk to a human. I ended up creating a Twitter bot to tweet at the Gmail team every 12 hrs or so complaining about how I couldn't recover my account even though I had it for 10+ years, and about three days later, they responded and helped me through a streamlined recovery process that helped reset my password.

You don't need to create a Twitter bot like me, but I would try tweeting at @gmail or @google once a day until they respond. Good luck!