Microsoft Test Manager cannot install test agent on these machines

I am trying to create a new environment using microsoft test manager. Unfortuntely I get the following error:

Microsoft Test Manager cannot install test agent on these machines. Possible causes: - Machines are not running or they are not available on the network - The File and Printer Sharing exception is not enabled on the machines.

Controller is up and running , the user and password is correct. Firewall is disabled. File and Printer sharing exception too.

I do not know what is going on. How could it be solved? Do not know how to go further with this.