Hi @alexvanini_5999 ,
I would try using the Inedo Agent instead; if you are getting this error, it most certainly means that there is some kind of security/hardening/account setting that is blocking WinRM. This is the underlying technology that PS Remoting and the PowerShell-based agent use.
In this state, it's a real pain to get working - and the Inedo Agent is much more stable, anyway. It will not be "randomly blocked" by a new GPO or Patch Tuesday bug as we've seen a lot with WMI.
Otherwise, you'll need to scour the web for obscure settings that may have been applied to the server. You may see information logged on the target machine under Windows Event Log under Windows Logs → Application or System related to WinRM.
It's possible that the domain account lacks needed rights, even though it's a local admin. Sometimes subtle rights (like SeRemoteInteractiveLogonRight, etc.) can block initialization.
Good luck, let us know what you find!
Thanks,
Steve