ok, here is my suggestion. find out how to remove the keyboard. there is usually a strip or panel that pops off then you have a few screws and the keyboard lifts up.
CAREFUL NOW!!! the keyboard is connected by a thin ribbon cable, make not of how it is routed and folded and connected. Most keyboards use a sliding connector, open the connector and remove the keyboard.
now tip the keyboard on its edge and tap it, any hair and dirt should fall out. take some canner aire and blow down each row of keys.
Replace the keyboard and retest... if it works, it works, if still does not work, get on ebay and buy a new keyboard.
My F5, F7 and Windows key quit working.... the two most used keys... I need F5 and F7 in my DJ software to get back to the music library, and the windows key is obvious.
I ordered a new keyboard before i blew my other one out, the new one did not fit cause the ribbon cable was too short.... but after i blew the old one out it worked