Hi and welcome.
This is an easy fix as I have done this on my V
You need to carefully prise the rubber cover off the button.
Underneath you will find a short plastic spigot that extends down onto the button switch deep in the instrument cluster
Take this out with tweezers and don't loose it.
Then spray copious switch cleaner / WD40 down the hole, as the switch becomes stiff / dry / gummed up overtime
Then resemble and it should work.
- If you do a search you will find posts detailing this in greater detail with pictures EDIT 2
- use a small screwdriver (or nail file) to get the flange of the rubber button back into position.
Make sure you get it all the way inside otherwise the button might not work. It should make a click sound as you push it in.