getUrl returns "internal exception"

getUrl returns "internal exception"

I want to get a json list of items from a webservice:

map Campaign.listSibCampaign()
{
      mapheader = Map();
      mapheader.put("api-key","Ab7XXXXXXXXXXXcaJ");
      resp1 = getUrl("https://api.sendinblue.com/v2.0/list?page=1&page_limit=2", mapheader, false);
      return resp1;
}

This works fine with Postman
I get this
{
    "code": "success",
    "message": "Successfully retrieved list details",
    "data": {
        "lists": [
            {
                "id": 689,
                "name": "[4922 - totale] ACCESSOIRES DE MODE",
                "total_subscribers": 2180,
                "total_blacklisted": null,
                "open_rate_percentage": 0,
                "click_rate_percentage": 0,
                "list_parent": 604,
                "entered": "2015-03-13 10:41:34",
                "camp_stats": null
            },
            {
                "id": 688,
                "name": "[4921 - totale] ACCESSOIRES DE MODE",
                "total_subscribers": 6627,
                "total_blacklisted": null,
                "open_rate_percentage": 0,
                "click_rate_percentage": 0,
                "list_parent": 604,
                "entered": "2015-03-13 10:24:12",
                "camp_stats": null
            }
        ],
        "page": 1,
        "page_limit": 2,
        "total_list_records": 527
    }
}

But with Zoho Creator I get this error

Executed Successfully
Return Value: 
{responseCode=-1, responseText=internal exception}

Thanks in advance for your help