Thunderbolt Ethernet Self-Assigned IP

Hey guys!

So earlier today I bought a USB ethernet adapter, as last night the shared Wifi in my apartment complex was going extremely slow (and i noticed there was an ethernet cable coming through the wall). I didn't realise the adapter I bought was a 10/100, which was fine as the internet capped at 100MB but seeing as the connection is 1GB it made sense to buy a better adapter from the Apple Store a 10 minute walk away. So I bought a gigabit thunderbolt ethernet adapter, came home, unplugged the other one and got the "self-assigned IP" issue. After deleting the usual plist files, smc reset etc. I plugged the USB one back in and it's also giving me the same error too. The Wifi connects with no issue, it's just strange the USB adapter worked straight away and now it doesn't! I've trawled through many recommendations but i'm stumped on this one! Maybe it's a router issue, but I don't have access to the router here officially (I could go out into the hallway and open the panel that it's in and reset it, but there's another 5 residents here).

Any help would be appreciated!