Windows 10 – Can’t open Device Manager “This app has been blocked for your protection”

uacwindows 10

Problem

Running a new Windows 10 Enterprise machine with all updates (1803) and whenever I try to open the device manager (or other programs like it), I get a UAC pop-up dialog saying "This app has been blocked for your protection" with only a close button.

uac warning

When I click on the link "Show information about the publisher's certificate" nothing happens.

This issue occurs when logged in as an administrator type user or when logged in using the built-in Administrator account. I am looking for the root cause of this issue and an appropriate fix (I already have a workaround — below). There are several similar questions on Super User, but they are either a) very old, or b) only suggest the work-around.

Current Workaround

Currently I run a cmd console as administrator and enter the program name as a command and it just works. Besides being inconvenient, it leaves me wonder if something larger is broken here.

NOTE: I have another Windows 10 Enterprise machine I created 10 months ago with the same DVD, also updated (1803) and it does not exhibit this behavior.

Other approaches

  • Disabling Windows "Smart Screen" as shown here does not work.
  • Creating another user profile does not work.
  • Disable defender (virus) scan has no effect.
  • Changing the ownership of mmc.exe to myself instead of TrustedInstaller is a hack which shouldn't be necessary as the Administrator group already has read & execute access.

Best Answer

I know it might be a bit late but i just fixed the exact same issue you're having by disabling Admin Approval Mode and the built-in admin account viaw GPEdit security policies.

Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options. At the top is the admin account policy but scroll to the bottom and you'll see UAC policies. Disable Admin Approval Mode restart your pc and see if it fixes it.

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