Make sure you have all the drivers loaded for the alternate video card you want to use. It should have been supplied with the card.
All I could think of that cause the problem is the high-speed cable I recently bought on Amazon, but that doesn't sound reasonable. I used that new cable only for 4-5 hrs on Friday. However, my monitor got no hdmi signal on Saturday when I tried to boot it on. When I switch to onboard graphics card of my motherboard, my monitor got back hdmi signal. Afterward, I had tried the method which unplugs the PSU power cord and held the case power button for 30 sec to 1 min, however, my monitor still got no hdmi signal.
Motherboard: ASRock z75 pro3
GPU: SAPPHIRE Radeon R9 280X
Memory: 4x G.SKILL DDR3 2400 4GB
PSU: EVGA SuperNOVA 1000 PS
CPU: i5 2400

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