Canon MG7500 series Online Manual page 733

1002
Cause
Printable disc (BD/DVD/CD, etc.) is not set.
Action
When printing on printable discs, use the disc tray supplied with this machine ("J" is on the upper side).
Place a printable disc on the disc tray, attach the disc tray to the machine, then tap OK on the touch
screen.
Possible causes include the following.
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