Not sure I can help much, but I was jsut fighting that this evening.
All of the sudden it fixed itself, but I'm not sure what steps exactly did it.
This is what I think fixed it.
I made sure the old package was un-intalled.
I did a clear on the Nuget Cache
I did a clean on the solutions. Closed the IDE and reopened.
I I did a rebuild all and it built.
Painful.