Why is my replacement screen inoperable?

Hi,

Following my recent display replacement, the display does not operate properly. I see white and pastel back light colors with dark vertical and horizontal lines; no logo. The lines move about, especially when using hardware buttons or touching certain areas. All of the hardware buttons (power, home, etc) seem to work. When plugged into the wall, the phone gives the familiar double vibration, and I can hear Siri saying "screen locked". I wait a few minutes but no repeated vibration commences. The phone is recognized by iTunes when I connect to PC by USB. I've performed the soft reset routine. I have followed the instructions on the iFixit Help Center page for "iFixit iPhone Display Assembly Has Vertical Lines/Bars". I have soaked the logic board in 91% isopropyl alcohol even though it shows no visual signs of corrosion anywhere.

I've visually checked my work twice, meaning I've stripped the phone apart 3 times looking for defects in flex cables and on the logic board. I have not been able to find any. I followed the guide in a detailed manner, so I am unsure what to do at this point. The original display worked great despite some old water damage. It wasn't cracked or anything, I only replaced it in hopes that it would improve the phone's poor battery life (which a new battery from iFixit barely improved: full charge lasts 12 hours). My previous repairs, although few, have gone well. I've broken a flex cable on two different accounts but was able to identify, order, and replace it without exception (power flex and headphone jack flex). I'm a novice, but not a jackass.

All my online research says the display is bad and has to be replaced. I'd hate to replace it to find similar issues. If you have any ideas, please send my way.

Thank you!