fixed : Canon scanner “Cannot communicate with scanner” error in macOS 10.15 Catalina

Question :

I have been using my Canon CanoScan 5600F scanner for many years with my Mac, and it has always been working great. However : now, in macOS 10.15 Catalina I keep getting error messages that the scanner cannot be found…

The exact error message is this : “Scanner reported an error Cannot communicate with scanner for these reasons: – Scanner is turned off. – USB cable is disconnected. Please check and try again.”

Sometimes I manage to get things working by replugging the USB-cable and switching the scanner OFF and back ON, but that solution doesn’t last…

What can I do to solve this ?


Answer :

even though Canon does not list support for your the CanoScan 5600F for macOS 10.15 Catalina, the Canon driver that used to work in MacOSX 10.7 Lion through macOS 10.14 Mojave still works in macOS 10.15 Catalina, so if you do not have this driver already, download it here

NOTE : this solution is tested to work for the Canon CanoScan 5600F scanner, but will probably work as well for other CanoScan and LiDE scanners that run into the same problem and error message

To solve your problem, do this :

  • go to Apple-icon (top left in the menu bar) and click on “System Preferences” from the pulldown menu
  • in the “System Preferences” window, click on “Printers & Scanners”
  • in the list on the left, at “Scanners”, select your CanoScan scanner
  • then, click on the Minus-button at the bottom of the list on the left, to delete the scanner from the list
  • now, switch OFF your scanner and unplug the USB-cable from the scanner and from your Mac
  • then, go to Apple-icon (top left in the menu bar) and click on “Restart…” from the pulldown menu
  • when prompted, UNcheck the option to reopen all open windows and restart your Mac
  • then, plug the USB-cable back into your scanner and your Mac and switch your scanner back ON
  • when your Mac has restarted, open System Preferences
  • in the “System Preferences” window, click on “Printers & Scanners”
  • in the list on the left, at the bottom, click on the Plus-button
  • in the window that opens, select your CanoScan scanner from the list and click the “Add”-button
  • you can now select your CanoScan scanner from the list on the left and click on the “Open Scanner” button on the right to open it
  • now, the “Scanner” window will open and you will be able to scan

You could be okay now, but you still might encounter this ‘Cannot communicate with scanner’ error again… in that case, do this :

  • click the OK button in the pulldown window that reports the error
  • then, option-click (right-click) on the scanner icon in the Dock
  • if your Scanner icon is not always visible in the Dock, do this first :
    • in the popup-list, select “Options”
    • in the next popup-list, make sure that there is a checkmark at “Keep in Dock”
  • now, close the Scanner window by clicking on the red button top left
  • then, reopen the Scanner window (by clicking on the scanner icon in the Dock)
  • now, the Overview Scan (preview scan) will start automatically as expected
  • if not, just repeat this process a little slower than you did before 😉

Note 1 : it seems like this problem is caused by macOS 10.15 Catalina cutting off all USB-connected devices when it puts your Mac in sleep mode (at the moment of writing there seems to be no simple way to adjust this in macOS…)

Note 2 : if you cannot live with getting this error once in a while, and you cannot wait for Apple and/or Canon to come up with a definite solution… have a look at the VueScan scanner-app

That’s it !

enjoy 😉