Bob's right, when this happened to me, it was because one of the cables wasn't properly connected, so here's what to do:

1) Save all your work to an SD Card/Floppy/

2) With the KN7 switched OFF take out all
connected cables.

3) Clean/dust and re-connect them.

4) RESET THE KEYBOARD as follows:-
Whilst pressing the three lower left
buttons in the RHYTHM GROUP section -
(60's & 70's, MODERN DANCE and SOUL & R&B)
at the same time, turn the POWER ON.

Hope this works for you.

Audrey