Facebook Marketing API – Cannot Create Ad-Set – Facebook api

I’m new to the facebook marketing API.
I was able to create a campaign.

But it seems I cannot create Adset.

I’ve tried posting with Javascript to the Adset:
https://graph.facebook.com/v2.8/act_156221465583672/adsets

with this payload:

    var targeting = {
        "age_max": 43,
        "age_min": 18,
        "geo_locations": { "countries": ["US"] }
    };

   var campaignId = "520337003094784508";

    var promotedObject = {
        'application_id': 2242592062246511            
    };

and post body:

    {
        "access_token": accessToken,
        "name": "testNirAd",
        "lifetime_budget": "8000",
        "autobid": "true",
        "start_time": new Date("October 13, 2017 00:00:00"),
        "end_time": new Date("November 13, 2017 00:00:00"),
        "optimization_goal": "POST_ENGAGEMENT",
        "billing_event": "IMPRESSIONS",
        "daily_budget": "2000",
        "campaign_id": campaignId,
        "targeting": JSON.stringify(targeting),
        "status": "PAUSED"            
    }

But I get this error:

     {
         "error": {
         "message": "Invalid parameter",
         "type": "OAuthException",
         "code": 100,
         "error_data": {
         "blame_field_specs": [
             [
                "name"
             ]
         ]
       },
       "error_subcode": 2061015,
       "is_transient": false,
       "error_user_title": "Required Field Is Missing",
       "error_user_msg": "The name field is required. Please complete the          
       field to continue.",
      "fbtrace_id": "HFg4HmwbQhG"
   }

}

Which is strange because I have a name field.

Then I’ve tried the same with the Javascript SDK
https://github.com/lucascosta/facebook-js-ads-sdk, with the same payload data,
and this time I get:
{
code:1
fbtrace_id:”DcXmP0Wr82Q”
message:”An unknown error has occurred.”
type:”OAuthException”
}

Please can anybody help?