Use a needle to insert into an edge and pry up.

Did you reconnect the antenna behind motherboard?

You need to replace the screen

Have you tried to reboot by pressing power button and volume button down?

I had this problem before with my oneplus one. I too replaced the screen recently but that has nothing to do with the battery...When you get a message that your battery is to low to start up it means that you need to let it charge for at least an hour. I didn't even have a charging light indicator until about an hour..then it turned on.. good luck.

Screen connection is on top by the camera. F.Y.I if you didn't touch the screen connection then it's not the issue..