Q: Cannot scan from Canon MG6120 after upgrade to OS X El Capitan

Hi,

See if downloading and reinstalling the driver for OS X v10.11 El Capitan helps > https://www.usa.canon.com/internet/portal/us/home/support/details/printers/suppo rt-inkjet-printer/mg-series/pixma-mg6120

Ttry System Preferences > Printers & Scanners > Scan tab > right-click in the left sidebar > select Reset printing system.

Sometimes just reinstalling the printer/scanner drivers also helps. Download the most-recent version from Canon support website.

Are you connecting to the printer/scanner wirelessly or by cable?  If it's wirelessly try using a USB cable. If you're using a cable try a different port on your Mac or a different cable. 

I'm having the same problem but a Canon MX310 model. I've reinstalled the most updated drivers and now can at least print but not scan. There used to be a 'SCAN' button on the UI but it's now gone. Is this an Apple thing or a Canon thing? I'm so irritated that every time I'm forced to do an upgrade that I lose programs, apps and even hardware capability.