Anyway, without wasting any time let’s see How to fix the underlying cause of this issue using the below-listed troubleshooting guide. Therefore, not able to turn on this feature could be a serious problem. There are many reasons for you not being able to turn on Windows Defender in Windows 10 such as third-party Antivirus might be interfering, Windows Defender is turned off by group policy, incorrect date/time issue, etc. One thing we need to understand that Windows Defender provides complete protection to our system. Why can’t I turn on my Windows Defender? # No matter what reasons are behind this problem, we will walk you through the methods to solve this problem. Sometimes the main issue is that if you have installed a 3rd party Antivirus service then Windows Defender will shut itself off automatically.

Also, if you go to Settings > Update & Security > Windows Defender then you will see that the Real-time protection in Windows Defender is turned on but it’s greyed out and also everything else is turned off and you can’t do anything about these settings.

Turn on windows defender antivirus