ENTER-PSSESSION fails, client not trusted

To enable remote PowerShell session on a client, the client must be trusted.

You might get a similar error message thrown, when using enter-pssession COMPUTER

PowerShellError

The easiest way to get a computer trusted is:

  1. Enable Trused Hosts group policy for Windows Remote Management (WinRM) using gpedit.
    1. Open gpedit.msc and navigate to: Computer Configuration\Administrative Templates\Windows Components\Windows Remote Management (WinRM)\WinRM Client
    2. Set the  Trusted Hosts setting to enabled
    3. Add the IP of the client machine to the TrustedHostsList value, or use * (Asterix) to enable all clients

TrustedHosts

Run a gpupdate /force to reload the group policies. After that you should be able to start a remote session with the client.