I mean, if you open up Windows Explorer and type in \\ubuntuboxhostname
(replacing ubuntuboxhostname for the name of your Ubuntu machine) does
it list the printer amongst any folder shares?
I'm just wondering if for some reason the smb.conf file might have been
altered and your printer share removed?
I will have a look at that. When this problem first arose, many moons
ago, I was advised to add a line 'Listen *:631' to ports.conf /etc/cups
and this sorted things out. However, this time I cannot find a file
labelled ports.conf. I did find some files ending .conf and added the
above line in the appropriate place there but this has not put things
right. Your mention of smb.conf reminded me. Where or what is smb.conf
please. Remember, I am not very clever with the computer.