Problems connecting to ethernet with El Capitan I have a late 2013 MacBook Pro running El Capitan 10.11.6. Recently I bought a USB-to-Ethernet adapter so that I could connect to Ethernet. It was working fine, but now it's not after a few days. 

Now, I don't see the Ethernet option under "Network Preferences", and I tried resetting my NVRAM (as I've seen on some other suggestions online) but that didn't work. 

Any clue as to how I should proceed?
As mentioned in the comment, try the adapter on a different machine to see if it's still functional.

Have you tried to add a new network device in the network settings pane? The USB adapter should show up there.