Bootloop after screen replacement.

After replacing LCD/Digitizer and putting phone back together I started up the phone. Black apple logo over a white back drop appeared, the screen blinked and went to the low battery image. (picture of empty battery with just a red sliver). Seeing how the phone hasn't been used in a few months I assumed that the battery was probably just dead. I plugged it into the wall charger and as it was charging the phone would loop from low battery to boot logo to illuminated blank screen and repeat.

I let it charge overnight with no change. So I tried to put it into DFU mode. There was no "connect to itunes" image. I plugged it into the comp anyway and itunes detects it in DFU. I download and restored iphone but near the end of the installation of the new ios I get an error code stating that the iphone could not be updated.

I checked all the connections/screws for the fourth time. Inspected ribbon cables, home button etc. I purchased a new battery and installed it with no change... Am I missing something here?

TL;DR

New screen - didnt work

DFU iTunes - got error

Computer connects to phone

Checked all screws/cables

Replaced battery - still doesn't work