Unable to add Gmail account(s) to iMac

Hi,

I am unable to add additional accounts to iMac (2019) on OS Monterey.

I currently have my iCloud account setup in Internet Accounts, and I'm trying to add in the Gmail ones as well.

When I try to add the account by clicking on the Google logo: I get a popup window with loading progress wheel (not the rainbow spinning wheel) that never stops. I don't even get to type the email address.

When I try to add the account by clicking on the "mail account" option: I get to type in my gmail account, press "sign in", but I get the error message "unable to verify account name or password" and I receive an alert from Google. I have then gone into my google account (through another device) and marked the iMac device as secure, tried again but get the same result.

Please note I currently have multiple Gmail accounts correctly logged in and synced across 2x MacBooks, iPad and iPhone.

I am only coming across the issue with this particular iMac.

Am I missing something obvious?

Any suggestions are greatly appreciated.

Thank you!