Phone won't turn on?
replaced the battery and might have broken the flex cable between the power and volume buttons would that explain why it wont turn on? phone shows charging but is unresponsive to button input.
The power + volume flex needs to be replaced if it has been damaged.
That's possible i would try a different battery if you have one and then go to the flex cable. Usually you can see the damage to that unless it's one of the contacts. If neither work than you might have damaged your logic board.