After searching forums, search engines and websites, I found a solution on my own.
The answer is kind of embarrassing.
I tried these things first:
Direct connection via ethernet to laptop; I can print from the laptop without issue. Afterward, I removed the connection but the network couldn't see.
Rebooted entire system. No change.
Reconfigured printer through system settings. No change.
Ran diagnostics from various locations. No change.
Unplugged and plugged printer back in five minutes later. No change.
Checked for driver updates and applied updates. No change.
Uninstalled and re-installed printer. No change.
Disconnected from Internet and turned off firewall. No change.
Consulted owner's manual. No answers, no change.
Restored system to a previous point where the printer had been working. No change.
Reconfigured the printer through its control panel and menu, trying wireless and wired configurations with various options on TP and IPV6 settings enabled, disabled, and changed. No change.
Scrolled to bottom of printer's menu setup. There, not mentioned anywhere, is an option: Reboot Printer.
What? Unplugging it and turning it off doesn't reboot it?
I'm embarrassed that I didn't go directly to that printer and sort through ALL of its options. Stupid of me, and I'm always telling people to do that sort of thing. Look and think.
Well, at least it's fixed - and I probably won't forget how I 'fixed' it in a long, long time.
Causes Michael Seidel Supports
Kiva, Women's International League for Peace and Freedom, Propublica.org, Doctors Without Borders, GreaterGood.com