apple logo flashe then phone dies after battery and screen replacement

I recently replaced my iphone 6 battery and screen. after I did this the phone does not power on. when I plug it into the charger the phone turns on for a milisecond, turns off, and then turns back on for a milisecond, and this loop continues until I unplug the device. When I hold the home button + power button nothing happens. When I hold the home button and connect to itunes the phone starts to restore but then I get an error 9 message. I even went as far as putting the old screen and battery back in the phone and yet nothing happens.