trip computer button not working

[dwood100]

hi i need some help
ive recently bought a 03 peugeot 307 sw se 2.0td after bringing it home i realised the trip computer button on the end of the wiper stalk isnt working the display is stuck on how many miles before i need to fill up does any one know what the problem could be or if you can pull the button of and check any problems any help would be appreciated thanks darren