https://news.ycombinator.com/item?id=45968731

  Why can I not authenticate into Google Antigravity?
  Google Antigravity is currently available for non-Workspace personal Google accounts in approved geographies. Please try using an @gmail.com email address if having challenges with Workspace Google accounts (even if used for personal purposes).

https://antigravity.google/docs/faq

I love how being a paying Workspace customer for a decade or more has actually locked me out of so many Google products and features.

Not that I have any desire to try this at this point, but it's always felt ironic.

Thanks. Actually did use my personal account and got the issue nonetheless.

Same

Same

To save others the trouble, it doesn't matter whether you use Chrome or Safari for the auth flow. It's broken on both. (I'm using a personal @gmail account.)

Had the same issue, have been able to sign in finally using a Google Cloud Identity (former Workspace) account by changing my IP via a VPN to Singapore. No idea why, but that worked. Tried a few other countries too, but only had success with Singapore.