Outlook Addin Error: Not loaded. A runtime error occurred during loading of COM add-in

Question

I have created an VSTO Outlook addin. The configuration is as follows:

• Visual Studio 2008
• Office 2007 Outlook add in (3.5 Framework)
• MSI created using Visual Studio Setup Project
• Deployed to Office 2010 under windows 7

It works fine on the Dev PC however it fails to load once installed on the test machine. The outlook addin window shows a "Not loaded. A runtime error occurred during loading of COM add-in"

It is my understanding that I should not need to install any PIA as the Office 2007 PIA are part of Office 2010.

So far I have tried the following:

• set VSTO_SUPPRESSDISPLAYALERTS however it does not show any messages when it tries to start.
• configured Fuslogvw.exe (Assembly Binding Log Viewer) however it is not showing any binding errors.
• set VTSO_LOGALERTS and it is logging all alerts however as none are shown this has not helped.

Is there anything I am doing wrong or need to do in addition to make this work?

Solution

Make sure you have the VSTO 3.0 Runtime installed on the test machine.

You will also need to install the VSTO 3.0 Runtime Service Pack 1 if you are running Visual Studio 2008 Service Pack 1.

VSTO 4.0 Runtime is not required in your situation because it is used with add-ins created with Visual Studio 2010. Please note that the version of VSTO and runtime generally must agree with the version of Visual Studio used to create the add-in.