When you connect to the server or monitor, it has the connected symbol () on the Monitoring page. If the connection is lost, the server or monitor will have the disconnected symbol ().
If ReadyAPI cannot connect to the server, the monitors are also unavailable, so both the server and monitors will have the disconnected symbols.
You can check the connection to the monitor:
Select the monitor. The Editor is shown.
In the inspector on the right of the page, click Test connection.
ReadyAPI will try to connect to the monitor and display the connected symbol if the connection is successful and the disconnected one if it failed.