Why is my screen still black?

After cracking my A12 cell phone, the phone's screen would sometimes go black while using it. However I could still hear noises coming from it. For example, I would be watching a video and the screen would suddenly go black. I could still hear the video, but I couldn't see the screen anymore. I tried holding the bottom volume button and power button for 10 seconds, but nothing's showing up on screen. I also held the top volume button and power button too and it failed to work. My phone is still vibrating, so I know it's on especially when the alarm is on. However nothing is showing up at all now.

After replacing the screen, the screen wasn't black, but the problem was the same as before. The screen turned on, but it still went off when viewing a video or browsing a website. I noticed that when I tapped the bottom half, it instantly went black. What could be be the problem?

I also want to note that it currently won't even show up the logo or anything else anymore currently. Any help would be appreciated.