My HP printer is showing a 'Supply Error' even though the cartridges seem full. What could be wrong?

A 'Supply Error' can be caused by improperly installed cartridges, faulty cartridges, or issues with the printer's sensors. Ensure the cartridges are properly seated and locked into place. Try removing and reinstalling each cartridge. If the error persists, the cartridge itself may be defective, requiring replacement.