Clears all options to skip loading added to VSPackages by users wishing to avoid loading problem VSPackages, then starts Visual Studio.
The presence of a SkipLoading tag disables the loading of a VSPackage; clearing the tag re-enables the loading of the VSPackage.
The following example clears all SkipLoading tags.
Devenv.exe /ResetSkipPkgs
Reference
Devenv Command Line Switches