Unity update from 5.0.1 to 5.1 raised the following error with FB plugin.
This problem will repeats when new unity version is released but there is no new fb sdk yet.
Full error message text:
Unable to verify assembly data; you must provide an authorization key when loading this assembly.
c__Iterator0:MoveNext() (at Assets/Plugins/Facebook/Scripts/FB.cs:423)
Could not securely load assembly from https://integrated-plugin-canvas-rsrc.fbsbx.com/rsrc/unity/lib/sdk_6.2/CanvasFacebook.dll
c__Iterator0:MoveNext() (at Assets/Plugins/Facebook/Scripts/FB.cs:427)