facebook ads api – read other account campaigns – Facebook api

I am using Facebook ads api to read campaign from other account. I have created the application, got app_id and app_secret. In graph explorer, I am using other person’s access token and account id to get his campaigns. But facebook gives me following error:

{
  "error": {
    "message": "(#274) The ad account is not enabled for usage in Ads API. Please add it in developers.facebook.com/apps -> select your app -> settings -> advanced -> advertising accounts -> Ads API. Account 1817273581872129 not enabled for this application.",
    "type": "OAuthException",
    "code": 274,
    "fbtrace_id": "GW38TMsIi1v"
  }
}

I did followed error instructions but still the same problem.

here is the url i am using in graph explorer:

act_12345566654/campaigns

However, when I use facebook ads api in python:
I get the following error:

FacebookRequestError: 

  Message: Call was not successful
  Method:  GET
  Path:    https://graph.facebook.com/v2.8/act_1817273581872129/campaigns
  Params:  {'summary': 'true'}

  Status:  400
  Response:
    {
      "error": {
        "message": "Invalid appsecret_proof provided in the API argument", 
        "code": 100, 
        "type": "GraphMethodException", 
        "fbtrace_id": "FRdlngO8f04"
      }
    }

Here is the code:

session = FacebookSession(self.app_id, self.app_secret, self.access_token)
ads_api = FacebookAdsApi(session)
adaccount = AdAccount(self.account_id, api=ads_api)
campaigns = adaccount.get_campaigns()

Where am I going wrong ? Kindly assist me