Chosen Solution
Changed two batteries with iFixit battery kit. First iPhone 6 worked perfectly. Second iPhone 6 will not power on at all. Nothing comes on screen. Will not connect to iTunes. Replaced all cables and screws as instructed. Right now iPhone is completely dead.
well usually, this is the symptom of tech error. from the information i have gathered in your posts; the device was working properly. you opened the device, and tested the battery function closed the device, and it stopped working. In my shop, i would follow the steps below. -Test another battery: Plug in the old battery, see if that fixes the issue. If it does, then you would need to order another battery, as it shows the battery has gone bad. if its still not functional with a known working battery, move on to the next step -Scan the board for physical damage: chipped components/blown components, scratched PCB, etc (A microscope REALLY helps in this phase.) replace as needed. -anything further is likely ESD, or internal component failures: Electrostatic discharge happens while not taking proper preventative measures. (Anti static tools and mats) You can also short out a device with your Drivers, or connectors by accidentally connecting two nodes in the circuit.
