[Updated] Mac Book Pro (2015) Only one thunderbolt port works

[bigsmile01]

I have a MacBook Pro (mid 2015 model) where the logic board was recently replaced. I just noticed that first thunderbolt port doesn't work, when I connect an external display to it.

However, I only get this issue under MacOS. If I boot into Windows, it seems to work fine.

because it works fine in Windows, I am guessing it's a software issue.
Any ideas how to fix. I only recently reinstalled MacOS after the logic board was replaced, so I am not sure what it could be.

 

[jav6454]

How recent? If done within 90 days (if I'm not mistaken, else 60 days), then the work performed and parts replaced are covered under warranty by Apple.

Take it to them.

 

[bigsmile01]

So an update on this: I took the Mac back to the store. They examined it and found it needed an internal cable replacing. They tested it and said it worked fine.

However, I’ve taken it back home and it’s the same issue: Thunderbolt port 2 will work perfectly with the official Apple Thunderbolt to VGA or Ethernet or DVI adapter. But Thunderbolt port 1 doesn’t seem to work at all.

As before, if I use Thunderbolt port 1 in Windows, the Thunderbolt to VGA adapter will work (although the picture is cut off). But Ethernet doesn’t work. Thunderbolt port 2 works fine.

Any ideas? Thanks!