How to fix it when the product prompts "Your device is sleeping now".
1. Make sure the device is supported by the product. You can go to the link to check the supported devices.
2. Restart your device or reconnect the USB cable to wake it up.
3. If it doesn't work, you can tap Settings>Developer options>Stay awake for 4.0 system and Settings>Applications>Development>Stay awake for 4.3 system or below.