Replaced dock connector, still doesn't charge.

So after buying a second hand iphone 4 last year I noticed it was in worse shape then mentioned in the selling info and shortly the lock button stopped working. Well when I replaced that i noticed the screw for the battery connector was missing and so when i finished had to reassemble it the way i had found it.

Anyway a short while ago my charger has been playing up leading me to angle, balance and do all sorts to get the iphone to charge and it would only charge with one of my cables and not others. Well it finally stopped responding to any cable or angle so i bought a replacement battery and dock connector and set to work once they arrived. Opened up and put back just fine and both cables seem a lot more snug then previous however it still doesnt charge? The battery works and I have just one last go with 73% left. Any ideas why this thing still refuses to charge?