Hi Amit,
Seems connectivity issue. For the receiver 3rd Party please check:
1. Is the Port, firewall / network connection opened to connected to 3rd Party?
2. Are you able to launch the 3rd party URL in IE from your Client / PI network
3. Test with the same payload using 3rd party tool like SOAP UI and see the response. Use the tool from the Client domain/network (not from your local system).
Regards,
Azhar