You have the wrong token type, you generated an app access token aka Server to Server token. This is a “server token” and as the error says you need a “user token”
You need a user access token.
An App access token doesn’t represent a user (and essentially can earn no useful scopes)
A grant_type=code not a grant_type=client_credentials, will will also need an oAuth loop since you need some webservery bits to run this flow (to recieve HTTP Get requests)