How to enable to get “Members.list” from YouTube API?

I run a YouTube channel and I'm thinking of creating a web application for membership subscribers only. Therefore, I wrote a code to obtain the membership subscriber list using Members.list in YouTube Data API v3 for linking.

First, I created an OAuth consent screen in the Google Cloud Platform and acquired the scope of https://www.googleapis.com/auth/youtube.channel-memberships.creator.

Next, after acquiring the token using the obtained OAuth code, I fetched to:

GET https://www.googleapis.com/youtube/v3/members

And here is the result.

{"error": {"code": 403,"message": "Access forbidden. The request may not be properly authorized.","errors": [      {"message": "Access forbidden. The request may not be properly authorized.","domain": "youtube.common","reason": "forbidden"      }    ]  }}

How to fix this error?