Did you use Nabu Casa URL? OR are you using a different method?
If so, it would be really helpful to know the format of the Redirect URL you used in the Google API.
This is in https://console.cloud.google.com/
Select the corresponding project on the top left drop down selector,
On the top center search bar write “API” and select “APIs & Services”,
On the left columdn select Credentials,
Under " OAuth 2.0 Client IDs" find your login (mine is called Web Application) and click on the pencil button to the right.
Under " Authorized redirect URIs" you should see the URI that points to your Node-RED authentication.
I don’t need the complete URI, just the format (i.e. https://xxxxxxxxxx.ui.nabu.casa/google-credentials/auth/callback) to be able to understand what could be failing here.
Thanks,
Rodrigo.