Could not load BinaryFormatter from mscorelib v4.0

Hello! Im using BinaryFormatter with a 2d Game and is not working on WP8, but works on editor on windows and mac Any idea?

The setEnvironment variable is not working as a fix

Real Windows phone 8.1 Compiled under windows 10 with visual studio 2015 Unity 5.1.2f1

Any help will be appreciated

Thanks!

Edit: Also works ok on Android