The keypad may be bad. Most often they go bad due to moisture from cleaners being sprayed directly on them or steam from the cooktop when the vent fan is not used.
They can also go bad when the unit is stored in an unheated environment where there's a lot of air temperature change (hot during the day, cold at night, etc.)
It may also be some residue on the connections where the keypad plugs into the control board. Unplugging then replugging the keypad can sometimes clean them.
In other cases, a new keypad is needed.
If you or a friend decide to work on it, we have *critical* safety, disassembly, and troubleshooting info at our site, which is linked at our listing here on FixYa:
http://tinyurl.com/yzjozk
You can find helpful exploded view diagrams and order parts by entering your full model number here:
http://tinyurl.com/gv383