While trying to scan an image on your Canon Printer from your MF Toolbox, you may get this error and the scanning fails.
This means that you are trying to scan using your Wi-Fi connection from a remote laptop of PC which is not directly connected to the printer.

The canon printers are by default set to scan from the computer which is directly connected to the printer via USB cable. So you will have to change this setting to ‘Remote Computer’ and then you can scan using any other pc connected to your network.
To change this setting do the following:
1. Press [Scan].
2. Select <Remote Scanner> with up and down arrows, and then press [OK].
The machine is now waiting for scanning.
3. Retry scanning in the application or MF Toolbox.