More information needed.
Did you check to ensure that the GPU is fully and firmly seated in place and all applicable cables are likewise fully and firmly in place? Do the motherboard's video ports (if any) work?
May indeed be a physical failure of some sort: not configuration or software related.
Perhaps GPU, perhaps motherboard, perhaps PSU....
Find the User Guide/Manual for the computer's motherboard and verify the meaning of the 1 long beep and 3 short beeps.
That said, please update your post to include full hardware specs and OS.