Gsuite, but I presume regular gmail would have the same behavior. If it helps, mine was from pixelfed@pixelfed.sdf.org with the subject: “Confirm Email”

I’m in the same boat, I tried to login awhile back and had issues (I don’t recall what they were), and attempting login today shows my creds don’t work anymore.

I hadn’t seen that there was an instance now so this inspired me to go check it out, thanks! I thought I had the same issue, but it turns out that the email was just getting tagged as spam seemingly because of no SPF, so DMARC fail.