I’ve got a recurring issue with my laptop, that even a recent re-install didn’t cure. Periodically, but thankfully not too frequently, when I attempt to print from within an application such as LibreOffice, none of my printers are listed. I haven’t got to the bottom of it yet, but I have a recovery step that doesn’t take much to perform, so it hasn’t become too much of a pain yet.
The quick remedy (but alas not the cure) is to execute the following in a terminal window:
sudo /etc/init.d/cups restart
Straight away my printers are back. I’ll dig deeper into it once I get a spare hour or two.