I had that happen, too — even after successfully receiving the passcode at my recovery address, and entering it, they still denied login. Presumably it's a bug in their system (being generous), but who knows when they'll fix it, if ever?

I currently have an old (infrequently used) gmail account, with a valid recovery email, that I cannot log in to at all.

I don't have (or want) 2FA set up for it.

I tried an incognito window just now, and same problem ):