Thanks for the explanation! At least its not me.
I was up half the night searching for a reason that an old (2003) HP Laserjet (with JetDirect ethernet card from ebay several years ago) ie cobbled together junk
suddenly and persistently responded Offline to windows but printed its test page fine from Printer Config.
This after trying out several ~$5 2005-era Print Servers and Switches yesterday, that I've accumulated and never got around to testing: Print Servers from TrendNet and HP (discovered this one is 10mb Ethernet max) and two D-link Switches. I finally reinstalled the little Linksys 1-USB, four Ethernet port combo switch (also a thrift store find under $5) that I've had in service for a couple of years at the printer table.
Somehow after getting each of these antiques configured (successfully!) I had switched off SNMP protocol in the LaserJet. After much research online I learned SNMP (which wasn't needed when I initially set up this home network in or before the XP era), became mandatory starting with Win7. I never heard of SNMP before and had no idea switching off odd protocols - Appletalk, Netbui etc was harmless but SNMP was fatal.
Ok, got Humpty Dumpty all back together running smoothly, looked in here this morning, and everything's turned red. "wth did I do to my system now????"
Glad to know it wasn't me. Doc thanks for the explanation!