Also try the Network → Ping Remote Agents feature in SwarmAgent and see what you get in the log. It should say something like:
1:16:39 PM: [Network] Pinging remote agents... 1:16:39 PM: RENDER-01 (User = BUILDMACHINE, IP = 10.1.10.145, Version = 1.7.4718.0) is currently Available, Unassigned 1:16:39 PM: RENDER-02 (User = BUILDMACHINE, IP = 10.1.10.146, Version = 1.7.4718.0) is currently Available, Unassigned