Thunderbolt Ethernet connection "not connected"

My ethernet cable is connected to my Sky Hub box and both the green and orange lights are lit showing that the ethernet cable is connected. However when I go to the network preferences, Thunderbolt Ethernet Connection is shown as "not connected". I have tried both my adapter and cable in my girlfriend's macbook and it works flawlessly, connecting as soon as you plug it in and there's no issues when you unplug and 'replug' it back in.

On my macbook pro (mid 2012) however, It won't connect at all. I've tried to blow out any dust / lint from the thunderbolt port, I've tried cleaning it and when I reconnect and restart my laptop it'll be connected for maybe 30 seconds before disconnecting. The one time it was connected for longer than 30 seconds (and therefore thought I'd fixed the issue), I tried disconnecting it and reconnecting and then it had stopped working.

Something to note - The thunderbolt port next to my charger appears to be unresponsive. Plugging my ethernet adapter into this port does not light up the cable on the Sky Hub. Only the thunderbolt port next to my USB connection seems to work. Dodgy ports? How do I go about fixing that?

I've tried the "fix" listed here: https://apple.stackexchange.com/questions/229103/how-can-i-troubleshoot-or-reset -a-thunderbolt-ethernet-adapter and it didn't work.

I've tried to change all of my networkd settings, changed location, etc.

I've also run through the process here: If the Ethernet connection on your Mac stopped working recently - Apple Support but I have a more up to date version.

I am currently downloading the beta version of Sierra in a hope that it'll fix the issue but other than this I am at a complete loss.

Does anybody have any other solution to this?