Unable to login into Google Internet Account for Mac Sonoma or Sync Contacts

Question

I am trying to login to my mac with a personal gmail Google account (not GSuite) that has 2-Factor enabled, so I can sync mail, contacts, and notes.

Previously, I was able to do this. However, recently Mac kept popping up a notification to re-login to the account.

When logging into the account, I can enter in my user name and password, then I am prompted for a 2-Factor verification. After approving the two factor (I have tried with the Gmail iOS pop up, Google Authenticator, and a text message), I get to the following screen (below):

When I switch my browser to default as Safari (per the suggestion in this question), I get to this next screen (below) and then get the same 400 error screen above.

Other things I've tried:

Tried logging out of Mac, updating to the latest version, removing icloud, and trying to add Google accounts see this Q&A - same outcome.

I've tried using an application-specific password such as mentioned here. The application-specific password won't work when trying to login to the Google pop up.

When I use the application-specific login (e.g. one email account for mail and notes and add one CalDev account using google.com as the server and an application specific password) to add the account, mail and notes appear to sync,but contacts don't appear to sync.

Answer 1

For those who are running into this challenge. Here is the solution I found and an aggregation of several others:

1. Trying turning off your VPN or anti-virus webshield: Avast was running on a web shield on my computer (compliance requirement) and was blocking the login with Google as "insecure." I diagnosed this by realizing that logging in with Google was broken on websites opened with incognito, but for some reason not on a normal browser. This was ultimately my problem. Nothing else.

Others have also mentioned in other posts:

2. Try setting your default browser to Safari: In my case, this got me further along in the OAuth flow, but not all the way.

3. Try a clean slate by switching default browser to Safari, removing your iCloud account, deleting any Google related passwords or keychain tokens saved, clear your browser history, and restart your computer: Add the Google account first.

4. Talk to an Apple Store employee for ideas: No joke. The potential VPN issue was surfaced after I walked into the Apple Store and described the blue shirt there the issue. Didn't even need to go to the Genius Bar and was able to try it out back at home.

Good luck to those running into this!