Tried doing a battery replacement and now my iPhone won't turn on

So before, this iPhone 6 Plus's battery would die really fast. So I assumed it was the battery the problem. I ordered a battery from this very site and installed it. After the installation of the new battery, the phone turned on for like 15 seconds, the apple logo showed up and my computer was able to recognize it. Then all of a sudden it turned off. It hasn't turned on again since. I've left it charging overnight to see if it would turn on the following day, but it hasn't.

I am using an authentic Apple Charger.

What could be he problem?