The issue is that the OAuth token you’re trying to use wasn’t generated by the Client ID you’re using. Either you have multiple apps and are using the OAuth token from one with the Client ID of another, or you’ve used some 3rd party token generation site with your own Client ID.
Also, you can remove the "Accept: application/vnd.twitchtv.v5.json" that does nothing in Helix and was only used by Kraken to specify the version.