Mystery app preventing Windows 10 shutdown after update.

Hi. I've had this same issue for some months - a phantom, unnamed app that's preventing shutdown. I'm not interested in a workaround to bypass the message because I'd actually like my PC to shut down normally OR to flag up a genuine app that is stopping it ... perhaps due to unsaved work.

If there is a Microsoft Tech or other guru on here who can guide me by using the notes below, I'd be very grateful. 

I've run all the tests recommended on this and other threads (System File Checker, etc) and they all come up clean. Then I checked the Windows Event Log as recommended on another thread. Using that, I believe I've found the problem. I just don't know how to fix it. The log shows an error flag immediately after an abortive shut down attempt.

Does anyone know if there is a change I can make to remove this error and allow the PC to shut down normally?

The messages in the log are:

Activation context generation failed for "C:\Program Files (x86)\Microsoft Office\root\Office16\lync.exe.Manifest".Error in manifest or policy file "C:\Program Files (x86)\Microsoft Office\root\Office16\UccApi.DLL" on line 1. Component identity found in manifest does not match the identity of the component requested. Reference is UccApi,processorArchitecture="AMD64",type="win32",version="16.0.0.0". Definition is UccApi,processorArchitecture="x86",type="win32",version="16.0.0.0". Please use sxstrace.exe for detailed diagnosis.

System

Provider

[ Name]

SideBySide

EventID

35

[ Qualifiers]

49409

Level

2

Task

0

Keywords

0x80000000000000

-

TimeCreated

[ SystemTime]

2020-02-29T21:23:34.207666100Z

EventRecordID

1270

Channel

Application

Computer

DELL-P07N6C3

Security

EventData

UccApi,processorArchitecture="AMD64",type="win32",version="16.0.0.0"

UccApi,processorArchitecture="x86",type="win32",version="16.0.0.0"

C:\Program Files (x86)\Microsoft Office\root\Office16\lync.exe.Manifest

C:\Program Files (x86)\Microsoft Office\root\Office16\UccApi.DLL

1

To everyone except Microsoft, it is called A BUG!

This happens to me to due TAGO Fences Program. I must shutdown the program before close the windows.

Thanks for the potential solution to my unknown app not allowing shutdown.  However, my results are the same--PC will not shutdown without forcing a shutdown.  The suggested "scannow" program ran to completion without any feedback statement.  Thanks again, HB

This what I posted earlier, and what worked for me, (still working).

After much searching, and trying many, many suggestions, this is what eventually worked for me:-

Run Windows System File Checker

Your Windows PC comes with an in-built system file checker utility program. It can scan your system files and let you know if there is some corruption over there for which you get smashed with the error message “Task Host Window Preventing Shutdown”. You must follow these simple steps here to run the Windows System File Checker,

• Press the Windows Logo Key + X from your PC
• From the drop-down list select the Command Prompt(Admin)
• Click on Yes if prompted for permission. It will open the elevated command prompt on your system
• Now, type in the following command and press the enter button
• sfc /scannow
• Then, wait until the System File Checker continues the process of scanning. Press Y if the program asks for permission to apply the fixes for your missing system files
• Finally, Restart your PC once again and check if you can get over the problem there

I found the above on a list of several suggestions, which are on the following link, but the above was what removed the problem for me.

https://silicophilic.com/this-app-is-preventing-shutdown-in-windows-10/