lg stylo 3 screen stays blank.? What the reason?

Try taking battery out for more than 20 hours and put it later. Most likely the problem is that you overheated the phone. If that doesn't work, either get a new display screen or another phone.

Visit lg service centre to know what the real issue is, you can change the display of the phone if needed.

Might be due to over heating of the mobile phone, just cool down the mobile, and restart it.

These are the simply way to do once your device is found blank..

1. Power off the device.
2. Press and hold the volume down and power button until the Android System Recovery screen appears.
3. Navigate using volume keys and select using the power key.
4. Select Wipe data/factory reset and confirm.
5. The device should automatically reboot or select the reboot option if it doesn’t.

Press and hold both the "Sleep/Wake" and the "Home" buttons at the same time for at least 10 seconds. When you see the home screen, release the buttons.