Screen doesn’t turn on after replacement

I’ve repaired many iPhones throughout my life and all of them have gone smoothly until today. I replaced my iPhone 8 Plus screen and it worked after I replaced it. I then continued to install the camera and found that one of the cameras didn’t work and so I left the phone on the table opened up until I could get a replacement camera for the phone. Later I reattached all the cables and found that the screen doesn’t turn on. I installed the old screen and it doesn’t turn on. When I connect to a computer it doesn’t recognize it at all as a device. Nothing happens when connecting to a computer. Right now when I charge it, it vibrates and then that’s it. I can move the silent ringer switch back and forth and then the phones vibrates but other than that there is nothing I can do. I did see a spark when I disconnected the battery with a plastic pick which didn’t make any sense. I tried resetting the phone but it seems when I press the power button the phone isn’t turning on. When I charge the phone it doesn’t make the charging sound. Any solutions?