worst iPhone problem:( wont turn on after screen replacement

im desperate at this point… my 6 plus had a cracked screen which was on iOS 11.4, I replaced the screen with a new one and nothing no power no display… replaced the battery, nothing. I was finally able to get it into dfu mode and update to iOS 12. STILL NOTHING no screen display, checked backlight with a light and not showing a picture. it is up on iTunes it will show the percentage the battery is at and its recognized but I cannot see anything going on with the phone. SOMEONE please help me I’m hopeless and don’t know what to do i’ve tried hard resetting and pretty much everything else in forums I’ve seen. I’m posting hoping for a miracle lmk ideas you may have…