I have raised a ticket but want to post a thread to raise awareness of this issue.
Unity has deprecated .net 3.5, however GameSparks SDK only runs on this version.
Running the game with this SDK leads to numerous errors on different platforms.
I find it shocking that it is not up to date with the minimum standards of Unity.
My suggestion, which is "unscheduled in the backlog" (I read that term a lot in the forum), is to make the SDK compatible with .net 4