I discovered this same issue, you are required to have a phone their auth system is bugged me.

I just set up google workspace and I didn't have recovery phone or anything,just password and recovery email. I didn't login for 1 week (life stuff). When I came back it allowed me to login but didn't allow any admin stuff saying it didn't recognize me and that I must use a known browser.

Well, that was the only browser I logged in with.

The solution was a weird thing where I was able to add phone recovery and authenticator, but then had to wait 2 weeks (couldn't use it). After that I performed authentication as usual.

It's horrible.