According to the manual, on page 153, it indicates either that the system can't detect a keyboard, or it can also indicate that it can't detect a graphics card.
Your motherboard doesn't appear to have integrated graphics so make certain that your GPU is seated properly and all power plugs are connected snugly.
Also take a look at the Debug Post Indicator (page 11, #21) and see if it's showing anything there.
EDIT #1:
Also take a look at this similar issue:
Hello When I boot up my computer the CPU light comes on for 2 seconds, then it beeps 5 times (apparently it means theres a fault with the CPU), then the VGA light comes on for 3 seconds followed by the BOOT light showing for 1 second. After this sequence it boots up normally and there are no...
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