Google Reseller Permission

If I want to build a reseller portal under my reseller account... How can I do? I've try to use the service account to build jwt for Oauth, and I can retrieve a auth token for access api(s). When I pulling a request like:

{ uri: 'https://www.googleapis.com/apps/reseller/v1sandbox/subscriptions',
  method: 'GET',
  headers: { Authorization: 'Bearer ya29.AHES6ZTCYDJH41adclj5AR8....JBQa3lM_ZXpLvdsm2J8' } }

And I always got return like:

{
 "error": {
  "errors": [
   {
    "domain": "global",
    "reason": "authError",
    "message": "Please make sure you are using a valid Google Apps account",
    "locationType": "header",
    "location": "Authorization"
   }
  ],
  "code": 401,
  "message": "Please make sure you are using a valid Google Apps account"
 }
}

It likes say my service account is not authorized to access the apps reseller api...(Because it is not google apps account, but... it create by a apps admin... ) But my admin account is already a permitted user, I use the admin to create project and create a service account to build jwt...

I don't know how to setup the permission for a service account. Help @@~

The final response from Google is... the Reseller API still not support "Service Account" (that applied from API console). Currently just support real user account, and I need to try other way to access this service... Hope the near feature will implement the related permission to service account! Thanks for help!