check if Windows Defender UI lock mode is enabled, run the command::

Get-MpPreference|select UILockdown

To unlock the Defender UI, run the command:

Set-MpPreference -UILockdown $false

1. Download the fix file from Microsoft Update Catalog: https://catalog.update.microsoft.com/Search.aspx?q=KB5007651
2. Run the SecurityHealthSetup.exe executable as an administrator. 

reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows Defender" /v
reg delete "HKLM\SOFTWARE\Policies\Microsoft\Windows Defender Security Center" /v
RMDIR /S /Q "%WinDir%\System32\GroupPolicyUsers"
RMDIR /S /Q "%WinDir%\System32\GroupPolicy"
shutdown /r