TBS6981 and MSI A75MA-G55

I currently have the tv card in the PCI-E x16 slot and it works perfectly (without the power cable). I added an nvidia card yesterday so needed to swap the tv card to another slot. I tried it in the x8 slot and also the x1 slot with and without the power cable attached and it wouldn't work. However, as soon as I put it back in the x16 slot it worked. I have the latest BIOS for my board and all the latest drivers. Is the card faulty or is it not compatible with this board?