I've updated my iMac to Sierra (which is a red-herring, see further update below) and since then reset my work password, so need to re-authenticate via
System Prefs > Internet Accounts. We use the OneLogin OTP system for 2fa.
So I go to Internet Accounts, enter my
password, and it accepts that then displays the OneLogin 2fa screen.
I hit the OTP send on my phone as per usual (I also have tried manually entering the code) and it accepts that and takes me to the 'remember' or 'forget' screen.
I click 'remember' and then it thinks, and then says 'Failed to authenticate with Google. Please try again later'.
This same process works fine on my MacBook pro running El Capitan.
update I have also tried deleting all the relevant tokens from my keychain, with no improvement
Further update As part of deleting all the tokens in my keychain that seemed to have anything to do with Google or my work, I've now managed to wipe my work account completely from both macs (yay iCloud). Alas Now I am having the same issue on El Capitan so it's clearly not a Sierra specific issue. I'll change the headline to suit.