Hi, I replaced the battery in an old iphone 5, the replacement went fine, no issues with connectors etc, but now the screen remains blank and nothing happens, no amount of different key combinations will get the phone to do anything.  I swapped out the new battery with the old one and still the phone is dead.  I checked the screen connection, and they seem okay.  I'm not new to this having replaced many screens and batteries, but this is the first that hasn't been successful....

any suggestions?