How long have you had the card? It might have blown you know!
Or could be a PSU issue or maybe your motherboards PCI-E Slot Problem!
We Need More Details, Like What PSU You Have,Rating Etc. And Your PC Specs Too!
Anyways here is what you Can Do:-
1. Take Out The Card And Try It On Someone Else's Computer!
If That Works Out, It Means Your Card Is Fine!
2.Change The PSU To A Higher One And See If The Card Runs On Your Setup!
If It Works It Means That Its A PSU Problem! If It Doesnt Then Its Your Motherboard's Problem! You Have A Faulty PCI-E Slot!