Windows 10 or 11 is highly recommended (macOS blocks manual firmware uploads).
Because HP actively removes old firmware versions from its official support pages, you must source the file from reputable third-party cartridge suppliers, printer repair forums, or web archives. Look for firmware versions compiled before the mid-2016 dynamic security rollout. Step 2: Prepare Your Printer and Computer Turn on your HP OfficeJet Pro 8620. hp officejet pro 8620 firmware downgrade new