While holding Stop, press and hold the Power button.
The (often labeled as ST-V6000.exe or similar) is an unofficial, third-party utility designed to interface with Canon printers at a deep, firmware-like level. While Canon service centers use proprietary software to reset internal counters and diagnose hardware, the V6000 tool emulates these functions for consumer use. canon service tool v6000
Once this counter reaches a pre-determined limit (designed to prevent an overflow that could damage the printer's electronics), the printer will lock itself down and display an error. The 5B00 error is essentially your printer's cry for help, indicating that its internal waste ink counter is full. When this happens, you cannot print anything. While holding Stop, press and hold the Power button