Chosen Solution

I disassembled and reassembled the phone following the iFixit instructions, but now the power button is stuck and I cannot turn the phone on. How can I fix this?

Most likely, you accidentally installed the button upside-down. If you install the button upside-down, it cannot make contact with the switch on the motherboard, and will not return to it’s original unpressed length. To fix this, see the power button replacement guide.