MacBook Pro not recognizing USB ethernet adapter in macOS, but does in Bootcamp
If it's the standard Apple ethernet adapter, I've run into this problem on a couple of different MacBooks. There are a few different things you can try in this thread on Apple's message boards, but the one that usually works for me is this one:  


in System Preferences > Network, create a new network location
delete all the network devices from the list on the left
re-add the ethernet adapter device
configure the rest of the new location as required, and use it instead of the one you were previously using


(Even with that working, I still have another annoying issue with the adapter: if I plug it in while the laptop is asleep, it's not detected when it wakes. Have never found a solution for that.)