Touch ID works but power button doesn't

Well… This is not a simple fix! If you are not using TouchID then you could just swap out the button assembly. But you must fully disable TouchID services and any use of TouchID, otherwise you won’t have access to that service or even your systems files if you encrypted the drive. MacBook Pro 15" Retina (Late 2016-2019) Power Button

The other way is to carefully replace the blister button part if that is the failure. Here’s an image of the part so you can see the switch.

You will need a someone with the needed soldering gear and skills to desolder the button and replace it.

You might find a piece of metal was placed where the dome of the blister switch hits within the uppercase has slipped off or maybe it’s needed here to offer a better surface. That assumes the buttons switch it’s self is working properly.