Why can I not charge after display replacement?

check the battery connection and inspect the dock connector flex cable for damage.

i have the same issue after screen replacement. where is the flex cable for the dock connector.

I have a similar issue I've replaced many iphone screens and this last phone i worked on has been giving me problems. I plug in the charger and the phone starts right up but won't work with the battery in I thought it was the battery but I tested the battery on a parts phone and it works fine so idk if there is a connector I missed not sure......

I have had this problem before. First remove the screw holding down the battery connection and the battery. Then there is that bigger screw under it, you need to make sure that is tightened all the way down. Reconnect the battery and make sure the connection sits flat. That should fix the problem