The button on the side of the hub between the ethernet and power port is the multi-function button.
Hold the button for about 1 second and let go. The hub will verbally report the current status of the system which includes the announcement of all open sensors as well as any existing trouble conditions.
Hold the button down for about 10 seconds and the hub will turn white. This indicates the hub is in manual learn in mode where it can receive programming commands from new devices to pair them with the Hub.