When using the Extensis Fonts Add-on for Google fonts, you get the following error message:
"drive.google.com refused to connect".
The issues is the Google account the Extensis Fonts add-on is associated with is not the default account set in your browser where the add-on was installed.
If you are using a work account ** or alternate Google account for the add-on in which the Extensis Font add-on was installed, it will not have the proper permissions in order to run.
NOTE **: The Google Add-on is intended for personal use for the following Google applications: Google Sheets, Google Slides and Google Docs.
To resolve this issue, sign-out of the current google account and switch back to the account in which it was Extensis Fonts add-on was installed.