Ok . if your (WiFi button ) is actually one of (F1 - F12 ) keys -- you might want to try pressing ( Fn ) Key with it
or if it is another button alone and not in your keyboard - make sure it is not broken
also some computers allow to run it again without the need for the button
you can see if there is Some WiFi mangement software installed and check if it can enable it ( most devices don't have this )
also you might want to check if it is disabled in device manger
to open device manger - press Windows key + R
or from start menu Search for RUN
in RUN -- Type the following command or just copy& paste
mmc devmgmt.msc
under network adapter --> you might find multiple devices - see the one with wireless , WiFi something like that...