I purchased this video card HIS Radean R7 360 2b

and installed it on this socket 775 motherboard with 3.0GHZ core 2 quad and 8GB ram

And all I got was one long beep and three short ones meaning that the motherboard does not acknowledge the graphic card.

I then tested it on another old system an Asus Pt6 socket 1366 core i7.

It worked fine. I even ran Passmark benchmark test and it was great.

I then swapped the power supplies on both system and that did not help.
Both motherboards are PCIe 2.0 16

Any idea why?