Release both buttons. The power light should stay steady, indicating Service Mode is active.
If you prefer to avoid unofficial software, you can try these steps: canon+service+tool+st+5510+free+download+install
: Allows reading and writing of printer configuration data. Release both buttons
Use the ST-5510 only as a last resort. And when you do, treat it like a bomb squad tool – one wrong click, and your printer is history. and your printer is history.