@plzhalp 

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More likely failing power supply. However CMOS battery could also be bad.  I would start with that.

DL2032 batteries are not expensive.

This model is from 2018 so the warranty is likely over as well.

the pc is a year old so that might be the problem 

Please see this thread: R8 power button not working 

Some solutions are inside, but it seems the only real solution is for DELL to update the BIOS and get the BIOS with the issue removed from Windows Update.

Re: Sometimes it works, other times it doesn't work.

If bios update introduced a bug to disable the power button embedded in power led controller 12 pin connector, I assume the button should be non functional at all times?

If OP report is accurate that the button works intermittently, it might be something else?

R8:  1 2 3 (4 5) 

pin 4-5 (pin 4+ pin 5-) are reported to be the power button (although there is more recent report of uncertainty on this). Try disconnect the 12 pin connector and short pin 4-5 momentarily.  If PC powers on every time using this jump start trick, psu still works.  Doubt CMOs battery died already in this relatively recent model.

Credit: https://www.dell.com/community/Alienware-Desktops/Aurora-R8-Case-Swap-COMPLETED/td-p/7707496/page/2

Odd. Mine just started doing this today too. I have to push it a bunch of times until it finally works. Thought it was the switch being worn, but this is rather strange that it happened the same day yours did..

Ok I don’t know it is a coincidence or suddenly some of ours power buttons just not working well, I got the same problem 4days ago.

There's are multiple reports of this issue, and they seem to fix itself with a bios rollback.

I don't think it is a wiring issue.

R9 here. My power button also not working well. Just press power button multiple times and it will power up. I thought it was a failing power supply (i had power supply replaced, under warranty, early this year), but now it doesnt seem like it.

running AWCC 5.4.9.0 and AWOC 1.3.54.1380. DELL-Admin>

I have the same issue on my Aurora R8. I replaced the battery and nothing changed, so I let it sit for two hours unplugged after holding the Test Power button (which works) to drain it. I then tried the new battery again and it powered on upon plugging in the power cord, but didn't boot, giving the error code for a bad battery. So I powered it off and tried the old battery, which had the same result. I then unplugged half the cables connected to the motherboard, as well as the RAM, powered on the PC again, turned it off and drained power via the Test Power button again, plugged everything back in, and powered it on again. It actually booted up, so unplugged the power cord, plugged in peripherals, and powered it on again by re-plugging the power cable. I didn't shut it off for a week and it worked fine (I just kept using sleep mode instead of powering off), and restarts worked fine, which tells me the PSU is 100% fine, it's just a bad bios update that broke the button.

Currently trying to power it on again so I can try to roll back the updates to where it works properly.

It would be nice if Dell/Alienware were to at least acknowledge their mistake with this issue and put out an actual update for fixing the root of the problem.