Hi there,
The license for the RAWS agent gets installed on your local media server.
You can do this through Tools --> and then run the licensing wizard.
Once the license has been installed, go into your selection list, and browse to where you have the remote server (User-defined list/Domain list etc). Right-click that server, and then choose Install Advanced Open File/Remote Agent (I think that is it...).
Then try backing up the server in question again.
Laters!