Hp 5550 deskjet not printing

This is typical cartridge problem.Which cartridge changed?This printer can print with the only one cartridge inside it, whatever which.Try this: Open cover put out color cartridge then close cover.If blinking stops replace color cartridge.If blinking continues put out black cartridge and put in color.If blinking stops replace black cartridge, if not stop replace both cartridges.
If this not help your printer has problem in carriage unit and need repair.