When you hit the button, does the recirc icon come on? If it doesn't, then the problem is most likely the button is not making contact, and you might be able to take it apart and try cleaning it with alcohol. If the icon does come on, then the problem is most likely the vacuum damper motor, lines, solenoid, or vacuum source for the motor that redirects the air. It could also be the actual climate control box causing the problem, but that's a lot less likely.
I wish I could be more help. There's just a lot of stuff that could be broken.