OAuth2 scope error: Data appears in backend but not on frontend"

Question

I am facing an issue where I am able to retrieve data on the backend, but it doesn't show on the frontend. The error message in the backend reads:

"You are receiving this error either because your input OAuth2 scope name is invalid or it refers to a newer scope that is outside the domain of this legacy API. This API was built at a time when the scope name format was not yet standardized. This is no longer the case and all valid scope names (both old and new) are catalogued at https://developers.google.com/identity/protocols/oauth2/scopes. Use that webpage to lookup (manually) the scope name associated with the API you are trying to call and use it to craft your OAuth2 request."

I am using OAuth2 for authentication, and I believe the problem might be related to the scope, but I am unsure how to resolve it. The backend successfully gets the data, but when trying to display it on the frontend, it remains empty.

What I've tried:

Checked the OAuth2 scopes and ensured they match those listed in the Google OAuth2 scopes documentation. Verified the API request on the backend and confirmed that the correct data is being returned. Tested the API response in the browser’s developer tools and the data is visible in the network tab. Looked at the response body and it contains the correct data. Checked the CORS settings to ensure no cross-origin issues. Questions:

Could this issue be caused by incorrect OAuth2 scopes? If so, how do I fix this? How can I confirm that my frontend is correctly handling and displaying the data? Are there any other troubleshooting steps I can take to resolve this issue? Additional Information:

The backend is built with python. The frontend is using js. I've also checked the developer tools for any errors in the console and found [any relevant errors]. Any help would be greatly appreciated! Thank you!