I need to make a POST request from API gateway to target server ( Hubject ) which expects client certificate authentication. Our API gateway calls are forwarded to proxy server first and then to target server. I have a certificate (.CER) issued by Hubject CA and also our private key. I have created pfx file (pkcs12) and import it into gateway keystore ( Manage Private Keys ). I selected this private key to be used by Route via HTTPS assertion ( right-click -> Select Private Key). Unfortunately it is not working. Am I doing something wrong? Is there our proxy server playing some role? I am able to get a proper response from Hubject when I make a call from POSTMAN using supplied .CER file + our private key.