Mac Pro Late 2013 Thunderbolt Bus 2 stopped working

on my Mac Pro late 2013, Im not able to use two of the thunderbolt pots. Specifically, my TB Bus 2.. I can plug in a device and it powers up, but doesn't recognize anything. I think it stopped working early on after I got it, but since I didn't have many TB devices, I used a working port/bus. Now I am in need of all my ports and this is now a real issue. Ran hardware diagnostics and got the error NDT001. Since there is power going to bus 2, I wonder if its really bad or some simple issue that I can fix myself. Don't want to send it in and pay a lot of money I don't have. Its not or hasn't been heavily used since I bought it a couple of years ago (new from Apple) so I'm not sure what is really going on -thanks!