I read about the print quality issues you're experiencing on your Officejet 4620, as the black ink is no longer printing. Please try the link below to troubleshoot the issue, and if the problem continues, contact HP to see about a printer replacement or trade up to resolve the problem.
Click the thumbs up below to show appreciation for my help! Click the "Accept as Solution" if I have guided you to a solution!
Contact HP: Step 1. Open link: www.hp.com/contacthp/ Step 2. Enter Product number or select to auto detect Step 3. Scroll down to "Still need help? Complete the form to select your contact options" Step 4. Scroll down and click on: HP contact options - click on Get phone number Case number and phone number appear