Please open your motherboard’s manual and check what this post code means. In general 8 beeps indicate a display error which leads to a video card issue. I would try reconnecting the video and cleaning its port. Does the cooling starts when you press the power button? Could you check if the PC works with another graphic card? If all runs fine, you may need to have your card examined. If it is under warranty, you should contact the seller.
Hope this helps