Screen won't turn on but iPhone is working (according to itunes)

I’ve searched but no one seems to have my exact problem so I’m putting it out there.

the TLDR version:

• replaced iphone screen and digitizer with ifixit part
• display won’t turn on but phone is working (according to itunes on mac)
• checked and rechecked connections everything seems ok
• forced restarts on iPhone don’t work
• looking for how to pinpoint the problem with no display

The longer version:

Nearly a year ago my iPhone 5’s battery swelled and popped the screen out (fairly common I hear). The screen was still working, but I had to replace the battery so it would go flat again. While doing that, I messed things up and cracked the screen (don’t ask) and so decided to replace it with one from ifixit. I’ve done this many times and even once on another iPhone 5 we owned.

Everything seemed to go as planned, but after my “fix” the display doesn’t turn on. Plugged into iTunes it shows that the iPhone is on and charging and I’ve even done 2 restores but no visuals on the phone itself.

Force restarts on the iPhone don’t work. I’ve also opened it up again and checked the screen connections, digitizer and everything seems in place.

I ordered this ages ago, and tried the lcd replacement in August, saw it wouldn’t turn on and got frustrated, so defective or no, I’m sure I can’t return it. I’m also not up for spending another $40 on this thing if there’s any helping it.

So my question to all of you: Is there anything else you think it could be? Is there some kind of trustworthy diagnostic tool (through a computer) that I can use to pinpoint the problem?

Thanks in advance for any and all help.