2020 MacBook doesn’t recognize Ethernet cable when plugged in

Hi, I’m getting really frustrated with my Mac and I have no idea how to solve this problem.

I’m living somewhere where my only access to internet is through an RJ45 Ethernet cable. There is a box in the wall that the cable plugs into—there is no way for me to reset this box.

I got a brand new MacBook Air less than a month ago. I have an Ethernet to USB-C adapter to connect my Mac to the Ethernet.

For the first couple weeks, Ethernet was working fine. Whenever it successfully connected, green and orange lights would come up on my adapter (see photo). A couple days ago the Ethernet started randomly disconnecting. The cable would be plugged in and connecting with the adapter (green and orange lights would turn on) but in my Network settings it would say “Cable unplugged.”

I’ve tested my cable and box on a friend’s computer and it worked fine, so I don’t think it’s a problem with the Ethernet cable or connection. I’m unable to test the adapter on someone else’s computer because I don’t know anyone with a USB-C. I truly don’t think it’s a problem with my adapter considering the lights are turning on suggesting it’s connected. I spoke to Apple support last night and they were unable to solve it. They had me delete the Ethernet from my Networks, but now since my computer isn’t recognizing Ethernet when I plug it in, I can’t add it back.

Both the MacBook and Ethernet adapter are no more than a month old, so I find it really hard to believe that it would be a hardware issue.

Does anyone know how to get my computer to connect to Ethernet again? I’m absolutely at the end of my rope. Thank you!!