Skús ho zapnúť týmto xindlom:

https://www.sordum.org/9480/defender-control-v1-9/

Alebo si sprav z textu pod perforovanou čiarou súbor v Notepad.exe s príponou *.reg, klik myšou, merge (spojiť) s databázou Registrov. (Reštart PC).
------------------------------------------------
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SecurityHealthService]
"Start"=dword:00000002

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\wscsvc]
"Start"=dword:00000002

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender]
"DisableAntiSpyware"=dword:00000000
"DisableRealtimeMonitoring"=dword:00000000
"PUAProtection"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\MpEngine]
"MpEnablePus"=dword:00000001

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender\Real-Time Protection]
"DisableBehaviorMonitoring"=dword:00000000
"DisableOnAccessProtection"=dword:00000000
"DisableScanOnRealtimeEnable"=dword:00000000

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender Security Center\Systray]
"HideSystray"=dword:00000000

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender Security Center\Notifications]
"DisableEnhancedNotifications"=-

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend]
"Start"=dword:00000003