Hi, Most probably your MICRO switch is gone it has to be changed and it is not so easy, I do mine myself but I am a technician, If you want to know if the MICROSWITCH is gone there is a procedger to test all MICRO SWITCHES on your keyboard if any of you want to know how Here is how to do it but be careful ok, just do what I am tellenig you "DON'T MESS AROUND WITH THE OTHER TESTING THERE IS OK.

This is the procedger but be careful save your work before you do it, not that it will destroy your work but as a safty Precaution.
HERE IT IS

Switch Keyboard on
Press GENERAL (which is Keypad No 9)
Pres F3 then F8 (one after the other)
Press ENTER

Than from the Screnn Select PANET TEST (I think it's F1)
that will take you to all the switches you have on your keyboard.
Now Press the octave button the + I think you said, If it doese not HIGHLIGHT the PANEL you have on the SCREEN It means it has to be replaced. And take it to a Technician that has done this job before on a WK8.