Problem:

Access is denied in all .msc extension even on the administrator account.

Solution:

Re-associating .msc files with the Microsoft Management Console (mmc.exe)

Navigate to the C:\Windows\System32 folder and right-click the eventvwr.msc file (or any .msc file). Choose ‘Open With’. If you see the Microsoft Management Console listed at the top of the next window, click on it to highlight. If you do not see the Microsoft Management Console, click Browse, navigate to C:\Windows\System32, and double-click the mmc.exe file. With the Microsoft Management Console or mmc highlighted in the Open With box, check the box for ‘Always use the selected program to open this kind of file’. Click OK and see if the issue is resolved.