Ok, click the firmware update button to update the z-wave stack on the hub. It will disappear when successful. After that shut down the hub from the settings menu. Unplug power from hub (at wall not the hub) for 5 mins. Power back up and reattempt adding. Also realize if it's not plus, you're gonna have to pair the switch close to the hubitat as non plus z-wave devices don't do network wide inclusion (pairing through repeaters)