Get AddIn loaded in an Isolated Shell application with new version

I'm trying to get an AddIn loaded in my Isolated Shell application with an updated version.  I updated my Isolated Shell application.pkgdef file, modifying the field for "ProductVersion" from "3.0" to "4.0".  I've an AddIn that could load in the application when it was 3.0.  The AddIn file content has:

<HostApplication>

<Name>Application Name</Name>

<Version>3.0</Version>

</HostApplication>

After I updated the ProductVersion to 4.0, I also updated the AddIn Version to 4.0 but it could not load.  In fact, maintaining the AddIn Version at 3.0 allows it to load.  What am I missing?

I checked the registry under the HKEY_CURRENT_USER\Software\Application Name and also find that the 4.0 and 4.0_Config key folders are all created.

How do I update the ProductVersion with AddIns load in the correct version?

I am using VS2010.