Sagar,
Hope you are doing fine! A couple of questions
1) Did you set a Static NAT or Port forwarding?
2) Did you perform a fw ctl zdebug on the gateway that performs the NAT process? Running it on the management may be a good idea too. You can add a | grep IP to narrow the search withing fw ctl zdebug
3) Did you perform a fw monitor to see if everything is being routed accordingly?
4) Just in case, you state that you can reach the NATed management and ping it. It would be great if you could test de endpoint connection from your host and in a different network (Not inside the management network neither customer).
Regards,