FWIW, I can't get into My GM account using the Firefox browser, but Chrome works. This has happened before on other apps/websites.
It also forced the 2FA "code" on me. Sent to my email address on file with them, which is OK with me.
In general, I hate 2FA where they force SMS/voice codes on you.
I don't have a landline, my cell tower coverage is dismal, and they won't send it to my email address, because most say "email isn't secure, but your smartphone is". Nonsense.
I've never had an email address compromised, or lost/stolen my laptop, but I've lost 2 cell phones, while unlocked, in the last 4 years.