Desktop Boot and Lockup

Hi,

Mine is a HP Omen obelisk desktop and I bought it 1 and a half years ago.

Now when I tried to turn on the desktop, the desktop first beeps for 8 times, and then makes a 2 long beeps + 2 short beeps combo for several times. No signals or image on my monitor. Pressing keys on keyword also won't work.

Before that there are some stories about how I get into this issue. Today in the morning i tried to turn on the desktop, but the monitor says "no hdmi signals". I tried somethings like re-connecting the cables and it finally works. After that, the desktop was working perfectly. However, just minutes after that, i found there's no sound for the desktop (There are sound when I plug in the earphone, but no sound when I took out the earphone). I went into "settings" and follow the instructions to diagnose the problem, and finally it asked me to restart the desktop to finish reinstalling something. I shut down the desktop and when I tried to turn on again, it started to beep 8 times then 2 long and 2 short as described above. The power light (that diamond shape symbol) is on and red, i can hear the noise from the fan, but there's nothing happened after that. No signals on the monitor, striking keys won't work, long press to shut down and restart also won't work.

I am sure the monitor is working because I connect to my working laptop and it displays the screen perfectly. I am now wondering what this beep means and what should I do next.

Best regards