Canon PRO-100S series Online Manual page 496

Disc Tray Jammed
Pull out the disc tray gently.
If the disc tray cannot be pulled out, turn the printer off, then turn the printer back on again. The disc tray
will automatically be ejected.
When the disc tray is pulled out, place the disc tray ("K" is on the upper side) again, then retry printing.
Place the printable disc properly referring to Placing a Printable Disc.
If the disc tray is still jammed, check if there is a problem with the printable disc.
Disc Tray Does Not Feed Properly
496