Then I realized what happened. Two routers / #Wi-Fi access points. When The computer connects to the closer of the two, the #WSD port decides the printer is "offline", even though I can view the printer's configuration web page with a browser. Went back to reliable TCP/IP port and multiple jobs flowed out of the print queue.
It's been a few years since I had to replace WSD (Web Services for Devices) port monitors to make printers work. Putting this back in my toolbox.
I guess it does. WSD uses broadcast messages, which are filtered at each network segment. I’m not going to open them up just because they couldn’t foresee and work around this issue.