How to enable and call External API's via Client Certificate Authentication in SAP BTP

[vetriver]

Trying to call a Concur internal API which requires Client Certificate from my Btp Iflow. I have created used the existing tenant certificate and used my cert's alias name in the client certificate authentication via HTTP Request call. but the Certificate is not being passed and dont see the CN name in the api-gateway logs. Please help me in solving how to use enable mutual tls via client cert authentication

THanks

SAP BTP Security