You are trying to get access from your acceptance environment to something else. What is that something else?
Do you have access to that something else from any other environment?
Is it possible to access that something else in any other way, soapui or postman?
Did you already play around by raising the loglevels? Depending on what you are trying to connect with set Webservices or RestConsume to trace. Otherwise use wireshark to see what is going on over the network locally. There are enough youtube video’s on how to inspect the packages.
Regards,
Ronald