I am developing a web application using Flask that needs to allow users to log in using their Google accounts. I’ve chosen to use OAuth2 for authentication.

I’m running into an issue where, after the user is redirected back from Google’s authentication page, my Flask application fails to fetch the user’s profile information. Instead, I’m receiving an error indicating that the access token is invalid or expired, even though I just obtained it.

Double-checked that my OAuth2 credentials (client ID and secret) are correct.
Ensured that the redirect URI is properly set and matches the one configured in the Google Developer Console.
Followed the OAuth2 flow step-by-step according to the Flask-Dance and Authlib documentation.
Attempted to refresh the access token but encountered similar issues.