OK more than a day, but there was a bad update where Apple accidentally blacklisted their own driver (ugh, I’m sure someone is getting yelled at right now). It should be fixed automatically if you are using the automatic update feature. Mine was broken at on Friday and fixed Saturday at 530PM, so software update is good.
You can kick off manual install but I had not realized you can check things by holding down the option key and clicking on the Apple menu and go to Software and look at the versions installed. Should be higher than 3.28.1 for things to work again.
Of course murphies law had me checking wired ethernet last night right in the window, mystery solved!