Verify that the 12V and GND pins are properly connected and there are no loose connections or damaged pins that could be causing a malfunction. Ensure that the IRIS A/M switch is firmly set to the ‘M’ position. Sometimes the switch might not be fully engaged, causing the lens to behave as if it’s still in automatic mode. Disconnect the power, wait for a few moments, and then reconnect it. This can sometimes reset the lens’s internal mechanisms and resolve temporary glitches. If the issue persists, it would be best to reach out to Canon support or visit a professional service center. They can provide more detailed guidance and, if necessary, service the lens.
