Hi all, I had trouble authenticating with Google Drive as well. It is pretty simple though.
In the settings, click “Need help?” then click “Authorization.” There is a URL in here that you will need to copy. Then click through to the Google API Console (there is a link.)
Create a Google API client ID if you don’t already have one. It will ask you for a product name (whatever you want) and a Google account (which you should have).
Click next through the steps. You will get to the point where it will ask you for authorized redirect URLs. You need to paste that URL you copied in here, but remove the s from the https:// – it did not work for me until I removed the s. It will generate a Client ID and Client secret which you can copy & paste into the Settings area of the backup plugin.
As soon as I did this it worked fine and my Google account showed up inside the plugin settings.