Did you find a solution for this problem? We're facing the same issue.
In the 5.00.8239.1000 release of SCCM .NET 2.0 version was depreciated and since the SCCM add-on targets .NET 2.0 it couldn't load the SCCM dlls in order to function properly. This issue is resolved n the latest version of the SCCM add-on 2.1.7.
Please download (the download link is below) and install 2.1.7 and this issue should be resolved