Fixed with 27766 Workaround for “Your organization used App Control for Business to block this app” dialog in the Canary Channel

After updating to Build 27764 in the Canary Channel, some Windows Insiders are reporting hitting the issue that previously impacted the Dev Channel where an “Your organization used App Control for Business to block this app” dialog is shown when attempting to use or install certain third-party apps on your PC due to an incorrect policy being enforced. The following steps should mitigate the issue:

1. Open Command Prompt with administrator privileges.
2. Type and hit enter: mountvol s: /s
3. Type and hit enter: del S:\EFI\Microsoft\Boot\cipolicies\active{8E8A94F0-6EB9-42C7-A189-E018C8CF3D10}.cip
4. Type and hit enter: del S:\EFI\Microsoft\Boot\cipolicies\active{36D62F7C-AB85-4F61-8724-744294F24023}.cip
5. Type and hit enter: del S:\EFI\Microsoft\Boot\cipolicies\active{66D7D265-7EDD-47DD-86E4-F7C42CD55A8F}.cip
6. Then reboot your PC.

If you are dual-booting between the Canary Channel and the Dev Channel or another version of Windows, you will need to do this workaround BEFORE booting to the other OS.

If the above steps do not work, you may need to disable Secure Boot first and follow these steps:

1. Disable Secure Boot on your PC.
2. You will be asked to enter your BitLocker recovery key.
3. Log in to your PC and open Command Prompt with administrator privileges.
4. Type and hit enter: mountvol s: /s
5. Type and hit enter: del S:\EFI\Microsoft\Boot\cipolicies\active{8E8A94F0-6EB9-42C7-A189-E018C8CF3D10}.cip
6. Type and hit enter: del S:\EFI\Microsoft\Boot\cipolicies\active{36D62F7C-AB85-4F61-8724-744294F24023}.cip
7. Type and hit enter: del S:\EFI\Microsoft\Boot\cipolicies\active{66D7D265-7EDD-47DD-86E4-F7C42CD55A8F}.cip
8. Reboot your PC once with Secure Boot still disabled.
9. Then reboot again and enable Secure Boot.

In small cases, your PC may not boot into Windows. To get out of this state, you can follow these steps:

1. Disable Secure Boot on your PC.
2. Then get into Windows Recovery, choose advanced boot options and disable driver signature enforcement.
3. Then do the above-mentioned workaround for deleting the policies after logging in.
4. Alternatively, you can also delete the above-mentioned policies directly from the Windows Recovery console.