Wait! don’t throw that GPU video card away or assume it’s dead, not working. Try this first.
Reset your motherboard CMOS, clear it by moving the jumper cable pin. You should have a manual for your motherboard if you don’t see the CMOS battery or jumper to clear it. You can look up the manual by google search your mother board model # usually printed on the mother board.
After you reset your motherboard cmos (DO THIS WHILE THE VIDEO CARD IS REMOVED and POWER IS UNPLUGGED). Place the GPU video card back and turn the computer on. Your computer should detect it. If it doesn’t then yeah there might be other issue.