telnet 192.168.1.xxx fwupdate -d -f /path/to/old.fu
(as Administrator):
: Some users report that even after bypassing initial blockers, the printer may hang indefinitely on a "Verifying" screen or simply reboot without actually changing the firmware version. hp officejet pro 8620 firmware downgrade hot
Downgrading the firmware on the HP OfficeJet Pro 8620 involves the following steps: telnet 192