Replaced proximity/power button flex cable and now won't charge

I replaced the proximity sensor/power button flex cable on an iPhone 4S. the power button now works, but for some reason the phone will not charge. other than the power button, the phone was very well taken care of. I did not even touch the charging port area! I checked for possible damage IN the port opening and it's clean as a whistle. We used MULTIPLE cables and MULTIPLE configurations (connected to pc via USB, connected to outlet with AC adapter), still doesn't charge. The battery was temporarily disconnected during the repair and reconnected only when testing and before closing the cover. I made sure the unit was completely turned off before disconnecting/reconnecting the battery. Battery and all parts/connections do not show any damage.

Another mystery is that when you plug it in, it recognizes that it's plugged in and shows all the proper charging indicators. Just doesn't really go up and battery drains as if it isn't connected.

What could it be? Any one know if this is a common issue? I've done this part replacement many times and this is the first time I've had this problem. Phone was working fine before the repair, so it looks like I'm going to be responsible for this. Please HELP!