TheExcelAutomator on Wed, 07 Aug 2019 13:53:35

My business develops an Excel COM add-in which is registered for the current user and has worked perfectly for over a decade.

Recently, some of our users are buying new computers with Office pre-installed as an app into this folder:

C:\Program Files\WindowsApps

For example, this appears to be the default Excel executable installation for the Excel app:

C:\Program Files\WindowsApps\Microsoft.Office.Desktop.Excel_16051.11901.20176.0_x86__8wekyb3d8bbwe\Office16\EXCEL.exe

Strangely, in some cases our COM add-in still loads and seems to work fine, but in other cases it's not even detected by Microsoft Excel as a COM add-in.

Furthermore, on the machines on which our COM add-in loads, it looks like Windows or Office is creating an entire copy of our application in the following folder:


Our software automatically installs into the following directory:


So it's very strange to me that a copy is being made of it in the local cache directory.

Additionally, our COM add-in writes settings to folders within C:\Users\[UserName]\AppData\Roaming, but these are automatically being added to the corresponding folder in C:\Users\[UserName\AppData\Local\Packages\Microsoft.Office.Desktop_8wekyb3d8bbwe\LocalCache\Roaming...

I cannot find any clear documentation regarding how we manage this seemingly random behavior when maintaining and deploying our COM add-in, or any assurance from Microsoft that the new apps-based installations of Office will not break traditional COM add-ins.

Our biggest issue is that our system installs (i.e. validly registers all COM objects and classes, etc.) perfectly on some computers using the Excel app version of Excel, but not others. I'm actually currently looking at 2 computers with the exact same version of the Excel app (Microsoft Store) installed (Version1907 Build 11901.20176 Microsoft Store) - as per below - and one machine works fine and the other does not even detect our COM add-in as being installed:

For the machine that does not work, our COM add-in is not even being included in the Application.COMAddIns collection in VBA, implying that it is not properly registered, even though we've confirmed that the registry setup is identical to the other machine.

Obviously something is different, but we can't seem to find it...

I have been researching this issue for a while, and found a number of other posts relating to it, none of which have been clearly addressed:


Can anyone provide me with some clarity with regards to how this new Office app/packages-based infrastructure is working, and how it should best be managed from a COM add-in installation, deployment and use perspective.

Thanks in advance. M.


Eugene Astafiev on Wed, 07 Aug 2019 14:13:23


There are a lot of issues with Microsoft Office installed from the Windows Store. You may find the  Office from Microsoft Store: a spreading source of issues article helpful.

TheExcelAutomator on Wed, 07 Aug 2019 14:41:10

Thanks Eugene, that's a helpful blog from Andrei Smolin.

However, it does seem to raise all the issues without providing workarounds, so the only takeaway I'm getting from it is to recommend that our users uninstall the Microsoft Store version of Office...

I really hope Microsoft clears this up, as it's become quite painful for us on a customer support basis...