While holding Power, release Stop and press it (or 6 for some newer models).
The is a specialized utility designed for maintenance tasks on Canon Pixma and G-series printers. While it is widely sought after for resolving the "Waste Ink Absorber Full" error (Support Code 5B00), it is not an official public release from Canon, which carries significant security and operational risks. Core Functionality canon service tool v5204 free download exclusive
Searching for a "free" version of this tool carries significant risks: While holding Power, release Stop and press it