The Knog Scout is a security device. It requires a bonded/encrypted connected. In this case the bonding is not correctly established. This can happen if the Bluetooth bond is forgotten in Bluetooth settings on the iPhone. Remove the Scout from the Knog app, your phones bluetooth list and FindMy app (if applicable). Perform a factory reset before attempting to reconnect to the Knog app.
Do not attempt a factory reset while your Scout is armed.