Hi and welcome to the community! Since you're new please be sure that you have checked out our Discussion guidelines.
Do you get any reaction when you press the ON/OFF button? If not, I suggest that you hold the ON/OFF + volume up(+) button for 10 seconds. Without trying to power on the phone, connect it to the charger via wall socket and let it charge for 1-2 hours. If the battery is completely flat, it can take a longer time before the phone powers on and/or indicates charging.
