I think you should pop the case open and see if you can push the button directly on the mobo, idk if you can get at it with just the rear shell off but if it functions then it very likely is your aftermarket case is no longer lined up, you might be able to manipulate it back or add a tiny shim or try putting the stock one back on. If it doesn’t function then at least you’ve narrowed down the problem. If you have a hot air soldering iron you might be able to apply heat to just the button area and it might reseat itself on the pins but I wouldn’t go down that road till after the warranty is up.