First I hade problem using spotifys API since GPT said it was different roots which led me to temporary use a URL-shortener. When successful the link said CLIENT ID MISSING which led me to include that value in the “Authorization URL” as such:
I am having the same issue while authorizing from googleapis except it’s “OAuth state invalid or not found”. the response is fine and the state is there. I have seen this posted on several forums and no one has an answer.
I have the same problem using AWS Cognito as the IDP. Used a URL shortener for the root domain issue then had to add Client ID and redirect_uri to the auth URL. Once I sign in I get redirected to the Main menu not my GPT and I get “OAUTH INVALID OR MISSING”