Won't sleep after digitizer replacement

I replaced the digitizer on the Galaxy Tab 4 8.0. The new digitizer works great, but now the tablet won't go to sleep now. Tapping the power button does nothing. I can bring up the power menu by holding the power button, but just tapping it does nothing. I tried waiting for it to go to sleep by itself, but it never does.

I'm not sure what happen in the repair process that caused it to behave like this. Any ideals?

EDIT: After messing around with it a while, it turns out it may have been a software issue. I had notice after replacing the digitizer and turning it on, that the date and time were off (only about 2 months behind not 1970-1-1). I'm pretty sure it was right before so I don't know what caused that. Also when I turned it off and just plug it up to charge, the power button would respond to a tap to show the battery status. That led me to conclude it was not a hardware issue but a software issue.

I told the customer the situation and that a full reset was the only thing I hadn't tried that may fix it. He was okay with resetting it, so I when into recovery mode and did a factory reset. Now it works fine. Only thing that still bothers me is why did this happen in the first place. I made sure the tablet was powered off before disconnecting the battery, so I don't understand how such a simple digitizer replacement would mess up the date and time and completely disable sleep mode.

TL;DR: Tablet wouldn't sleep. Fixed with factory restore.