license key issue

Hi
   We bought a Flexmonster license key for our domain ****.com,  and has been working with one of our server under www.****.com; and now we have grown and installed another server under ***.****.com ; both servers are for internal use only, they are not available through a pubic address; but when we tried to use the license describe above for our domain ****.com on the new server, it send us the following error: “Current key is only applicable for ****.com. Read more info about this error”; could you assist us pls. Thanks, Kind regards.
Boris Hernandez 
IT Manager