Why Real Time Protection is disabled and I can't enable it anymore

[Erez]

Firstly I tried "Reset This PC" feature but this didn't help at all.

Secondly I reinstalled Windows 10 directly by using the setup.exe of Windows 10.iso that was downloaded by MediaCreationTool20H2.exe but this also didn't help at all.

Thirdly I reinstalled Windows 10 indirectly by first installing Windows 8.1 and then back Windows 10 but surprisingly this also didn't help at all.

Why Real Time Protection is disabled and I can't enable it anymore? What keeps it disabled, greyed out and prevents me from enabling and turning it ON?

Do I need to buy a new PC with Windows 10 to have it enabled?

 

[BigFeet]

The only thing I can think of that would keep it grayed out is if you have a third party anti virus or security suite installed. On a clean Windows 10 install it should always be on by default.

 

[Erez]

The only thing I can think of that would keep it grayed out is if you have a third party anti virus or security suite installed. On a clean Windows 10 install it should always be on by default.

I had but I have already removed all third party anti virus and security suite installed already and it is still grayed out.
How do I clean install Windows 10 without any USB stick, flash drive and DVD?

 

[BigFeet]

I had McAfee on my HP, and it took running their removal tool twice before it removed every trace of it. Windows may still think it's installed. Whichever third party antivirus you had, they should have a removal tool. You can clean install Windows without a usb or dvd drive like this..... https://www.intowindows.com/how-to-clean-install-windows-10-from-iso-file-without-usbdvd/

 

[Erez]

I had McAfee on my HP, and it took running their removal tool twice before it removed every trace of it. Windows may still think it's installed. Whichever third party antivirus you had, they should have a removal tool. You can clean install Windows without a usb or dvd drive like this..... https://www.intowindows.com/how-to-clean-install-windows-10-from-iso-file-without-usbdvd/

I did this already. I have already verified that Keep Nothing is selected, but this didn't solve my problem at all! Real Time Protection is still grayed out!