Connection Error : SharePoint Connected System

Question

While trying to setup connected system for Sharepoint using Client Credential authentication system, we are getting the error as 
 
 We have used Sharepoint OOTB Conneted system and provided the Client Credential Authentication details like, instance URL,Application (Client ID), Client Secret and Directory( tenant ID). We have also obtained the SSL certificate for the sharepoint Online in PEM format and uploaded in Admin console-> Trusted server certificates. 
 Can anyone help resolve this error to establish the connection successfully?

Mathieu Drouin · Answer

Did you try putting it in Client Certificates instead? 
 Trusted certificates is for servers with self signed certs. Client certificates is for mutual TLS. 
 
 "Some web services require transport-level client certificate authentication when setting up an SSL connection. The Client Certificates tab of the Certificates page allows you to expose certificates for use by the HTTP integration and HTTP connected system objects, the Call Web Service smart service, the webservicequery() expression function, and the webervicewrite() expression function."