DIAGNOSIS The printer's internal page counter has reached a pre-set threshold, triggering a toner-end lockout. This does not necessarily mean the cartridge is empty.
FIX Perform a toner reset procedure. With the printer on, open the front cover. Press and hold the 'Go' button for 10-15 seconds until all LEDs light up. Release the button. Close the front cover. The 'Toner Life End' message should clear.
IF THAT DIDN'T WORK The reset may not work if the toner cartridge's internal chip is fully depleted or faulty. Try removing and firmly reseating the toner cartridge. If the message persists, the cartridge may genuinely be empty and require replacement.
HEADS UP The reset procedure will not work if you are using a non-genuine Brother TN-730 toner cartridge, as the chip behavior differs.