Your Mac will attempt to connect to the TOPMOST, Working interface shown on the list.
If Ethernet is not topmost, click the gear icon below the list of networks and 'set service order' by dragging Ethernet to the top. When it is not plugged in, like at home or the coffee shop, it will not be working, and will be ignored.
If Ethernet show up green with no error message, then it is working and you are connected.
If not getting any web sites, launch a Browser and enter:
1.1.1.1 and press return.
If you get the *CloudFlare splash page, you likely have a Domain Name Server (DNS) issue.
*CloudFlare is not part of the solution, they just have THE simplest numeric IP address.