iPhone 6s keeps charging, but doesn’t start
a couple of months ago I changed the battery of my current phone and I wanted to continue with changing my sister’s phone screen and sell it. I’ve taken the screen off, but then let it lay down for a couple of months. As a result there was a lot of dust on there and now I want to fix the phone again. I wanted to check the battery’s condition, but now the phone won’t start. It does show the battery icon when I charge it, but it stays like that for 2 hours. What could possibly be wrong and which steps do I take searching for a fix?