Release both buttons. The power light should blink and then stay solid green. Your printer is now in Service Mode. Using Canon Service Tool V5204 to Reset 5B00 Error Once your printer is in Service Mode, follow these steps: Open the Service_Tool_V5204.exe .

What is the specific or printer model you're trying to fix? Canon Support | Software and Drivers | Canon U.S.A., Inc.

licensed per computer. "Free" versions found on third-party sites often carry significant risks of malware or ransomware