Replacement screen doesn't work

My wife dropped her iPhone 6 and the screen started getting lines through it. It still worked and the glass was undamaged. I checked the ribbon cables but everything was connected. Although ironically after putting the phone back together her front camera and speaker didn't work so she had to make calls on speakerphone and only take pictures with the back camera. I bought an "OEM" replacement screen assembly with the home button and camera already installed on Amazon and followed the guide (I've replaced her phone screen or mine at least 4 times although not before on this model) and it all went exactly as planned but when I turn the phone the screen comes on like normal but the will go black and turn back on a couple times and then nothing. I have to remove the battery ribbon cable to get the phone back off. I'm guessing it's a defective replacement part. If it's OEM it certainly doesn't quite fit as tight, it fits really well but it doesn't have the same satisfying snap the original does. Any tips? Thanks