I post this just for the information that might be useful to someone with a similar problem. The troubleshooting took me many days; I'm not proud of that, but it may help others.
My Epson WF-4530, connected via LAN, had worked flawlessly with my iMac for years. Suddenly a few weeks ago, printing stopped working. The Printer Queue showed the software "looking for printer."
1 -- The printer queue applet showed the correct IP address for the printer
2 -- the printer worked fine with my other iMac and portable devices -- iPhone and multiple iPads
3 -- The Epson Printer Finder could find the printer, with the correct IP, address instantly
4 -- System/Printers showed the printer as "idle, Default" when it was online, and it showed it as "in use, Default" when a print job has been sent and while the print queue applet displayed "searching for printer"
5 -- If I turned the printer off and restarted it, the iMac found it for one print job, after which it reverted to "looking for printer" on further print requests.
I uninstalled the printer and reinstalled it with no resolution
I reset the Mac Printing System with no resolution
I upgraded from Catalina to Big Sur with no resolution
I had the latest Epson driver, and the printer worked with this current driver for several months before this problem arose, but I reinstalled the driver to no avail.
The printer firmware was "up to date."
I had installed the Epson driver rather than the Air Print driver.
I could find nothing whatsoever about this problem with Internet searches.
After a few weeks of pulling my hair out, it occurred to me to reboot the Netgear ProSafe Gigabit switch to which the Epson was connected. Thereafter, the printer is found and functions normally. I know little about the workings of switches, so I don't understand what was going on, but the moral of the story is not to forget about them when troubleshooting connectivity problems.
My Epson WF-4530, connected via LAN, had worked flawlessly with my iMac for years. Suddenly a few weeks ago, printing stopped working. The Printer Queue showed the software "looking for printer."
1 -- The printer queue applet showed the correct IP address for the printer
2 -- the printer worked fine with my other iMac and portable devices -- iPhone and multiple iPads
3 -- The Epson Printer Finder could find the printer, with the correct IP, address instantly
4 -- System/Printers showed the printer as "idle, Default" when it was online, and it showed it as "in use, Default" when a print job has been sent and while the print queue applet displayed "searching for printer"
5 -- If I turned the printer off and restarted it, the iMac found it for one print job, after which it reverted to "looking for printer" on further print requests.
I uninstalled the printer and reinstalled it with no resolution
I reset the Mac Printing System with no resolution
I upgraded from Catalina to Big Sur with no resolution
I had the latest Epson driver, and the printer worked with this current driver for several months before this problem arose, but I reinstalled the driver to no avail.
The printer firmware was "up to date."
I had installed the Epson driver rather than the Air Print driver.
I could find nothing whatsoever about this problem with Internet searches.
After a few weeks of pulling my hair out, it occurred to me to reboot the Netgear ProSafe Gigabit switch to which the Epson was connected. Thereafter, the printer is found and functions normally. I know little about the workings of switches, so I don't understand what was going on, but the moral of the story is not to forget about them when troubleshooting connectivity problems.
