That request you’re making is step 3 of the Auth Code flow, so it’ll do nothing for you without doing steps 1 and 2 first. Also you’re missing parameters.
These are 3 different Auth Flows Getting OAuth Access Tokens | Twitch Developers
The first 2 are for User Access tokens, the third for an App Access Token. If you’re making requests that don’t require user scopes, and are making requests on your server rather than in a frontend, the Client Credentials code flow is the process you should use.