I bought a GCP-700 this February. Recently, the sustain pedal stopped working. I troubleshot the problem by switching to a different pedal and confirmed that it's likely a connection problem within the keyboard. I have contacted the keyboard repairing branch of Casio Support via their phone number from this webpage https://www.casioca.com/support/authorized-service , got into the voice mail, left a message, and never got an reply. I just called them again via the same number this morning, got into voice mail once again.
Does anyone have any suggestions about what I should do, thank you!