02 Protege5 Overdrive not turning on..

When I press the OD button to turn the overdrive off which should make the light turn on , nothing happens...
It used to work but now the trans is stuck in overdrive for some reason..
The car shifts fine , no problems at all but the OD button does work.

Is there a fuse or something or is this a larger problem?

Thanks
Guys ....

Did you spill something on the shifter. The switch may have dirty contacts.