Check the body of the response, you should have an error message that will help explain what the issue is.
Also, I don’t think this will be the cause of your 400 error, but for all Helix endpoints the Authorization prefix is Bearer, not OAuth.
Check the body of the response, you should have an error message that will help explain what the issue is.
Also, I don’t think this will be the cause of your 400 error, but for all Helix endpoints the Authorization prefix is Bearer, not OAuth.