Did you try to browse to the WSDL with your (default) webbrowser? It should show the WSDL file, when you're authenticated correctly... if not, then this is probably the issue.
Yes I tried to open the WSDL in the browser it seems that WSDL files is loading in the browser even if the VPN is enabled. The WSDL is not hosted in the same server. When I disconnect the VPN it is getting loaded in the SOAPUI, but when I enable VPN it does not seems to load the WSDL for some reason.
It gives me below error
Error loading [https://abc.com/somefile/UserServices.wsdl]: java.lang.Exception: Failed to load url; https://abc.com/somefile/UserServices.wsdl, 0
