This error can occur when the license server or server machine is down. Re-verify that the AWR server is running on the specified server or the server machine is up.
If the server is running properly, another instance where you might see this error is if the port that you specified is closed. Port 27007 is open by default, however sometimes anti-virus and firewall software close this port. To see if this is the issue, you can download a port scanning software and have it try to communicate with the server machine on the port that is specified in your license file.