Thanks @Sander van de Velde | MVP . Below page
The device does not receive any messages from IoT Hub until it has successfully subscribed to its device-specific endpoint, represented by the devices/{device_id}/messages/devicebound/# topic filter. After a subscription has been established, the device receives cloud-to-device messages that were sent to it after the time of the subscription.
it means the device receive from a logic app which is sending messages to device. i mean if any Logic app with Cloud to Device persits, then only devices can receive it