LCD Dim and Touch Not Working After Screen Replacement

I am replacing the LCD & Digitizer on a Samsung Core Prime for Straight Talk (SM-S820L). I have tried two different screen replacements from two different vendors and in both cases the LCD is very dim on startup and the touch does not work. All connections seem fine, but I have not fully installed either screen. Like some other Samsungs, does the LCD and digitizer need to be fully installed to work properly? And/or does the digitizer need to be in direct contact with the LCD or frame? Does the LCD & digitizer need to be glued together?

The customer's LCD and touch were both working before the repair, just had a crack in the glass. I did remove the battery prior to any work, of course. I cannot seem to get this thing solved.

Any suggestions? Thanks in advance.