I have a Brother HL-5035DN networked laser printer for which I use CUPS on my OpenBSD desktop. I’d set up the printer over a year ago and there had been no printing problems during that time.
Three days ago CUPS suddenly refused to print anything even tbough I could still place files in the queue for printing. Nothing relevant had changed on my system as far as I could remember. I spent the next three days trying to get printing to work again, with plenty of help from kind people on daemonforums, but no luck.
After innumerable reconfigurations of the printer I decided to be radical: I deleted CUPS entirely and reinstalled it. No result.
At long last on the third day it occurred to me to delete the printer entry in CUPS and remake it. As soon as I’d done this CUPS started printing again.
I did think of trying that solution right at the start of the problem but I got side-tracked into other things,and forgot about it. Even when I remembered it I assumed,at first that reinstalling CUPS would automatically delete and reinstall the printer as well. It didn’t.
I still don’t know what the original cause of the problem was. One possibility is that I use the -current version of OpenBSD (similar to the unstable branch of Debian), which produces quite frequent updates for CUPS among other things. When this happens I’m supposed to delete various CUPS files after the update, but on a couple of occasions recently I couldn’t do this because the screen showing the list of instructions went blank before there was time to do so. Maybe this screwed something up.
Anyway, the moral of the story is that when a previously working CUPS suddenly fails, you should try deleting and remakikng the printer entry before doing anything else.