My phone does not turn on after following steps from YouTube.

Hi. So I have been using my iPhone 6s for over a year now and my phone just blacked out.

So basically, I left my phone in a room to charge (The room had air conditioner on, at 24°C). And then after a few hours my phone was not able to turn on.

Whenever I hold the power button at the side to see if my phone was actually low battery, no dice. I even tried to search YouTube tutorials on how to turn on a blackened phone.

One of the steps were to soft restart my phone, while the other is to apply pressure near the camera since the Logic Board might be dislodged.

But I followed these steps and nothing happened. It’s like my phone was already dead. Can you tell me whats the culprit and how to fix it?