Self-assigned IP address using ethernet

This is so frustrating! I’m on a Macbood Air, M1 and recently started using Ethernet with no issues for a week or two. Then suddenly I get no access due to a “self-assigned IP address.”

I followed instructions I found here for someone else and it worked… for a couple days. Now when I create a new location and put in new DNS Server numbers (as the instructions dictated), it reverts immediately to self-assigned IP when I “Apply.”

I’d really appreciate assistance to get to the bottom of this. My housemate is also on a MacBook and not experiencing this, wired from same router.