Lexmark MX721
From the home screen, touch Settings > Device > Maintenance > Configuration Menu > Supply Usage And Counters.
Select the counter that you want to reset.
Warning—Potential Damage: Supplies and parts without Return Program agreement terms may be reset and remanufactured. However, the manufacturer’s warranty does not cover any damage caused by non-genuine supplies or parts. Resetting counters on the supply or part without proper remanufacturing can cause damage to your printer. After resetting the supply or part counter, your printer may display an error indicating the presence of the reset item.
After replacing supplies, reset the maintenance page counter to resume printing.
This article shows the additional information required to escalate MFP usage issues.