My computer won't let me turn on the real time protection.

Good day! I'm Raniel, an Independent Advisor and a Microsoft user like you.

Can you try to restart the Security Center service as well as turn on real-time protection via command prompt
1. On your search bar, type command prompt and select "run as administrator"
2. On the command prompt window, type "services.msc" and press enter
3. Look for the service "Security Center" > right-click on it and select "Restart" > try to check again
4. If that didn't work, close windows security and go back to the command prompt window
5. Type the command PowerShell Set-MpPreference -DisableRealtimeMonitoring 0 or PowerShell Set-MpPreference -DisableRealtimeMonitoring $false and press Enter and check the status again.

Kindly check as well if you'll encounter the same issue when you enable the built-in administrator account:
1. On your search bar, type command prompt and select "run as administrator"
2. On the command prompt window, type net user administrator /active:yes and press Enter
3. Perform a reboot, login to your admin account and and see if you'll be able to turn on real-time protection

If the issue still persist, kindly perform a repair install of your Windows. I suggest that you watch the video on this article(https://www.tenforums.com/tutorials/16397-repai... or https://www.yourwindowsguide.com/2016/06/how-to...) for you to have an idea regarding the process of repair install.

I hope this helps.
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Thank you for your help but I came across several problems with this solution to...

- the restart button is greyed out so I can't click on it. (through services.msc)

- the command says " access is denied" when I types "net user administrator /active:yes" 

- the command says "You don't have enough permissions to perform the requested operation" when I types "PowerShell Set-MpPreference -DisableRealtimeMonitoring 0" 

Hi kogapyo,

Apologies if the suggested steps didn't work for you.

Have you also tried to perform the repair install instead?

Ok, this is really frustrating. I followed your advice and download Microsoft ISO for repair install and spent the past 6 hours restarting, updating, restarting again, and updating again, but the issue still persists. I don't want to reset my computer because I have important documents that can't be retrieved even if I were to download it into separate files...

Thank you for your advice though. 

Hi kogapyo,

Apologies if the suggested methods didn't work for you.

I'm running out of options here. Let's see if someone else has a better idea with regards to this issue.

Hello, I’m Virginia an independent advisor with 20 years of expertise in fixing my own & friends’ PC problems.
Which Windows 10 build are you running - 1903, 1909 or 2004?

When you uninstalled the other antivirus software did you also run their respective cleanup tool? If not then the remnants which have been left behind may be preventing Defender from starting.
If you post the names of the AV software I’ll check for removal tools.