A bunch of the solutions here didn't work for me, (e.g. sudo cupsenable and lpadmin -E).
If you're using Debian 8.6, Cinnamon 2.2.16 (Linux) do this from your GUI start menu:
Click Administration | Print Settings,
Then select your stalled CUPS printer,
Click Unlock (and give it your admin password),
Click Server | Settings,
In this click the blue "Problems?" link.
For Ubuntu 16.04:
Click System Settings | Printers,
Then Server | Settings,
Click the blue "Problems?" link.
This opens the printing troubleshooter. It will tell you what to do next.
Probably you will just have to check the Enabled property for your CUPS printer in your Print Settings. (You will need to unlock first).
Finally, to avoid this from happening again, change the printers "policy" to "retry-job" in the printer setup mentioned above (under properties | policies).
Fixed it for me!
What causes this problem: If my wifi printer is powered down when I print to a CUPS PRINTER, and my policy is "stop printer", then I get a message that I couldn't print and the printer is disabled (Enabled is unchecked). Only if the policy is set to "retry job" will Enabled not be unchecked. A few minutes after the printer is powered back up your jobs will begin to print.
(My other post about this.)