To check whether the Deployment Agent is running, check the state of the 'Red Gate Deployment Agent' service on the target machine.
To check connectivity with the agent, you can try pinging the agent from the machine that the Deployment Manager server is installed on. If that works, you can also try navigating to http://<your-agent-machine-address>:10301/ in a browser on the Deployment Manager server machine; you should see an HTML page that starts with the message:
This is a Windows© Communication Foundation service.
Metadata publishing for this service is currently disabled...
If the service is running but you can't reach the service page from a browser, the most likely reason is that a firewall is getting in the way. Port 10301 needs to be opened on the agent machine to allow the server to communicate with it.
As an aside, the misleading message about timeouts happens because we use WCF reliable sessions with message level security, and they retry operations until a timeout rather than providing useful error messages.