Canon Satera LBP-5600SE User Manual page 101

Align the circle mark on the lock release lever with that on the toner cartridge.
3
Remove the toner cartridge from the printer.
IMPORTANT
100
*Figure from the above
If the toner cartridge cannot be removed, check if the circle mark on the lock
release lever is aligned with that on the toner cartridge. If you try to remove the
toner cartridge forcefully, this may result in damage to the printer.
Align with this part