No snark intended: Replace it.
You give no information regarding the make/model of the laptop, which really needs to be offered if you want specific help.
If it happens to be an HP, they supply the service manuals on their documentation download pages for virtually every machine they make, and are one of the few manufacturers to do so as far as making these available to the general public.
There are some makes that have their power buttons on their own little PCBs while others are mounted to the motherboard. While it's not exactly what I'd call common, it's also not unusual for power buttons to "go wonky" with time, particularly if owned by an individual who's constantly turning the machine on/off or sleeping it via the power button.
I try to reduce my use of the power button on laptops to a bare minimum, using the UI to do things like sleep, shutdown, hibernate, etc.