Why is the power button not "clicky"?

I'm doing a full housing swap on an iphone 8, going well. Have done the volume buttons, they're clicky and feel really good. The power button though, yeah not clicky at all no matter what I try.. not sure what to do, it's as if it is constantly being pressed in so it's not possible to press it. Only other thing i can think of is to try the button mechanism from an iphone 8 plus, if they're even the same size, but I'm not keen on completely tearing that one down..