Calling Nintex service using my domain URL

Dears;
Good day to you,

I am facing an issue in calling Nintex service from my domain URL, however calling  using FE servers name it’s working.
EX.:
https://DoaminName/_vti_bin/Nintex.WCF/Nintex.svc/mex?wsdl      -- Not working
http://ServerName/_vti_bin/Nintex.WCF/Nintex.svc/mex?wsdl          -- working

please support on this argent, I am using it on all InfoPath forms connections.

best regards.