Prestashop 1.7.5 giving Bad HTTP Resposnce while getting customers through API

[Sady]

We are trying to read the customers,products from Prestashop versio 1.7.5 through Webservice

https://4idps-demo4.com/webservice/dispatcher.php. The Web Service folder is present but still we are getting the issue

PrestaShopWebservice Object
(
    [url:protected] => https://4idps-demo4.com/webservice/dispatcher.php
    [key:protected] => 1C1GKY5HFA4Z3I8W5CM8FFRZZYVCVSL1
    [debug:protected] => 1
    [version:protected] => unknown
)
PrestaShopWebserviceException: Bad HTTP response 

How to resolve this?