Test Remoting with its default configuration. If you’ve tinkered with that, undo your changes and start from scratch.
Start by attempting to connect from the initiating machine to the target machine by using something other than Remoting, but which is still security-sensitive. For example, use Windows Explorer to open the remote machine’s C$ shared folder. If that doesn’t work, you have broader security issues. Make a note of whether or not you need to provide alternate credentials – if you do, Remoting will need them as well.
Install a Telnet client on the initiating machine (a simple command-line client, like the Windows native one, will do). Attempt to connect to the HTTP WinRM listener by running telnet machine_name:5985. You should get a blank screen, and Ctrl+C will end the session. If this doesn’t work, there’s a basic connectivity problem (such as a blocked port) you need to resolve.
Use Test-WSMan using an alternate credential if necessary. Make sure you’re either using the machine’s real name as it appears in Active Directory. If that doesn’t work, you have a problem in the WS-MAN configuration.