well, its good that things happened this way because the work of isolating the bad component is already done.
I would take the time to double and even triple check that the card is seated properly and the power plug is inserted correctly. Sometimes these things can come loose while fiddling around with something else, or even just moving your case.
I don't typically work on my machine in the office, I have a workshop in the garage and I don't know how many times I've had a properly working machine in my workshop, but by the time I get it up the stairs and into my office, something has gone wrong.
If you are certain everything is seated as best you can then its time to start the rma process.