Why doesn't my replacement power button work?

I did the battery replacement kit but ended up slicing the ribbon cable to the power and volume button board. I ordered a new power button board here, and installed it, but it is not turning on the phone. When I plug it in, the screen lights up with the battery charging symbol — I just can’t get it to turn on. Is there any way to test if the power button board is working? Could there be some other problem which is causing it to not turn on?