how did I get self-assigned IP address

All of a sudden I could not connect to the internet via ethernet from my router. Wifi works, but direct wire connection is not working. I'm on a MacBook Air M1. Connection from router to USB hub via ethernet, and hub to Mac via USB-C/Thunderbolt connection. I've unplugged and reconnected with no change. I've not changed my setup and this all has been working for the several months I've had this Mac.

Looking in my Network System Preferences it says:

Status: Connected

USB 10/100/1000 LAN has a self-assigned IP address and will not be able to connect to the Internet.

Anyone know what is going on and what I can do about it? Thanks.