Printer Add button not enabled
Solution 1:
Try to open a terminal (or alt-f2 to display command execution prompt) and run
sudo system-config-printer
and check if you can add a printer from there.
Solution 2:
Open a web browser and navigate to http://localhost:631
. This is the real interface to your printing system. If you want to do anything fancy, do it here. You are eliminating a lot of potential error stemming from bugs and flaws in the gnome printer dialog. Mostly the gnome dialog is just oversimplifying on some advanced functions.
If you don't see a website on localhost:631
your cups daemon (the printing system) is not running at all. Make sure it is installed.
Solution 3:
sudo apt-get install cups
#my CUPS was not installed after upgrading to 18.04, after i did this printers showed right up just had to close and reopen the printer app