Black screen when turn on and capslock blinks 3 slow 5 fast

[nnkhanh]

I bought the HP ENVY 15-bq100 x360 Convertible PC back in 2018. I only used it when I brought it to school. At home I have my computer set-up so I didn't use it much.
  Couple months ago it started to turn off the screen while I was in class, couldn't boot it up (I missed out taking note that day). 
  Then I had to use my iPad for my entire semester. 
  I haven't touched the laptop until now since school is gonna start soon.
  The problem is still there. 
   My warranty is expired. 
  I looked it up the problem in manual, which indicates something 

3.5 (blink)

Hardware

The CPU is not detected.

   I never dropped or banged my laptop once. Now I dont know what to do. 
  Really tight with the budget because of Covid-19 also.  

  Please help! Thank you

[banhien]

@nnkhanh 

Please try a hard reset and see if it works.

1. Power off your laptop
2. Remove the a/c adapter, battery and everything that is attached to your laptop.
3. Hold the 'POWER 'button down on your laptop for about 10 seconds.
4. Plug in the a/c power supply (without battery) and power on.

Regards.

[nnkhanh]

The laptop I have is none removable battery unless you have to open the back of the laptop though.