Reverse Thrust Keyboard F2 assaingment

I have lost my reverse thrust f2 key assignments on the keyboard. In fs9 it now doesn't appear in the options for to manually change this action. In the knee board pad it is still listed as an assignment. I have looked at Microsoft help site and reloaded the config file by pressing alt + control as they suggested but nothing happened, no reverse thrust key. I am still able to obtain reverse thrust by using the throttles but an f2 key would be nice to have again. Can anyone suggest the procedures that I should use to correct in the re assignment of f2.