Answer to: Full cartridge but ink not printing.I have had this happen twice with my HP Deskjet 3510. I got on HP phone support and went through all the steps & tips both times and nothing helped. Finally, they suggested I try ANOTHER new black ink cartridge, and it worked perfectly. Apparently, the initial ink cartridges were defective. HP sent me a new cartridge and I mailed the defective one back to them.