Yamaha CLP 525 sound problems

I have a question about a digital piano. A Yamaha CLP 525 has sound when demo songs are played but not when any keys are pressed. I’ve tried a reset, replacing the power cable and making sure that local control is on by pressing demo/piano/c6. The manual has very few troubleshooting steps for this, all of which I’ve exhausted. Any suggestions?

You’re not going to like this much; the key-scanner is a programmed uController chip located on the middle board of the three key-contact boards underneath the keys. If that chip fails then the effect is what you experience.
Long shot - You could try reseating the connector C4 on the main board or removing the entire key frame and checking/re-seating the connector on the MK-M board (the middle one underneath the keys)
Best for you to contact a YAMAHA Service center to get that replaced - or if you want to try yourself the part number is: