AppArmor with cupsd denied in logs

Workaround from https://wiki.ubuntu.com/DebuggingPrintingProblems#AppArmor_Protection_of_the_printing_system

Make sure apparmor-utils is installed: apt-get install apparmor-utils

If you have any problems with printing, try deactivating the AppArmor protection with sudo aa-complain cupsd. Note after doing this I had to unplug and replug the printer for it to work.

You can re-activate AppArmor via sudo aa-enforce cupsd.

If this helps, look for messages containing audit in the /var/log/syslog file. These show which components are accessed by the printing system for which there is no explicit permission given in /etc/apparmor.d/usr.sbin.cupsd

More details in the above link. (They also want you to report the bug).