When cleaning, apply alcohol to the cloth, not the edges of the screen, because it might get inside the screen.

I had some success with using anti-static packaging, like iFixit parts come in.

It's less scary than it sounds. Just follow the directions and watch the connectors.

I like the method used in this video to block the battery. Seems superior to the instructions here.

Check the connectors. They're just metal pads, and if you got them dirty or oily (from your fingers) they may not be making contact.

This step is inapplicable on iPhone SE.

This step is inapplicable on iPhone SE.

@sam I deleted this step; that change should be denied, but this guide is confused; it involves a lot of steps that are not necessary if you are only changing the power button itself, but are needed to replace the Audio Control and Power Button Cable. This entire Guide needs to be duplicated and split. I'm willing to help with that.

You didn't connect the Touch ID cable properly. That's the best-case scenario, anyway.

I see no reason why you have to; just leave it connected and held by a soda can or something. It's just easier if it's out of the way, especially if the battery doesn't come free easily.