The OAuth 2.0 Authorization framework does not support content-types, such as application/json. Through Acquia ID, Acquia enforces the security posture strictly and follows the standards defined in the framework. Therefore, you must have the content-type header set explicitly to application/x-www-form-urlencoded when trying to access https://accounts.acquia.com/api/auth/oauth/token.

If you try to access https://accounts.acquia.com/api/auth/oauth/token with a different content-type header, you might get the following errors:

{ 
  "error": "invalid_client", 
  "error_description": "The client credentials are invalid" 
}

{ 
  "errorCode": "E0000021", 
  "errorSummary": "Bad request. Accept and/or Content-Type headers likely do not match supported values.", 
  "errorLink": "E0000021", 
  "errorId": "oae7U5DSFSgR5Kl3gSWcy-Ncg", 
  "errorCauses": [] 
}

In such cases, ensure that you use the application/x-www-form-urlencoded content-type in your token requests. For more information, visit Cloud Platform API v2 authentication.