Will not power on after replacing digitizer and battery

I replaced a digitizer and battery in an iphone 4s and after the repair the device would not power on. After further inspection i found that the power button ribbon had torn so I replaced it with a new ribbon assembly. I still have the same problem. It will not power on but when I plug it into the charger the apple symbol comes on for about 10 seconds and then goes off for about 10 seconds and then comes back on. I had another known good iphone 4s and swapped parts over to it and they work in that phone but not the one I am working on. Has anyone else run into this situation?