Can you explain in details how exactly you get this encrypted value?
Also I am not sure that packages appeared in Nuget gallery as a results of AppVeyor builds. For example 1.0.6 tag build failed the same way, but no package published. Package 1.0.0 exists in Nuget Gallery, but now AppVeyor build with that tag at all in the project history. It is probably some other action happened outside of AppVeyor build, which published those packages.