I mentioned this in the blog post comment thread, but I’ll add it here.
I cannot link accounts in Google Home. I click the add FAB, select hass.io, enter my credentials, then click Allow Access. I see a flash of a page that says ‘Accounts now linked’, then the flash message ‘Linking accounts’, then I get the message ‘Couldn’t update the setting. Check your connection’. HASS and my phone are on the same WiFi network, I am running HASS standalone v68.0, and there is nothing in the log to indicate an issue. I’ve never setup Google Home using the previous methods.
I got the solution (for me anyway) from the Blog comment thread.
Make sure that the username that you enter in HA cloud config and in Google Home is the same, including case, as it appears to be case sensitive. I had a capital at the start of my login name in Google Home, once I made it all lowercase to match HA it worked perfectly. Thanks to @virualdo for the fix!
Got the same sort of problem. Did work but after clean install I get the same error as OP.
Also another email address will not work then I have problems on the server. Login give authentication error. Delete cloud sir and restart doesn’t help.
Edit
Problem solved for me. The login needs to be exact the same. If you use a capital letter in your email adres in cloud login then this capital letter have to be on the Google assistant hass.io plugin login. Easily overlooked.