As other’s have said, this cable is super delicate.
When you replace it, make sure that the small metal handle it firmly reattached to the other side of the port. I thought I’d got it right first time, but had no video signal (thunderbolt detected display, and power was fed to the Macbook Pro).
I had to reinsert this one again, and one in, firmly press the connector home, then latch the handle over the other side. I also gave it a test pull to ensure it was secure. Then all was well!