No idea,
Both lit blend & lit premul work fine for me in a new project (2.5.1 & unity 5.0.0p3). Is lighting turned off somewhere / set to vertex?
Try it in a new project - I'd expect it to work, and then work your way back from there, thats the only thing I can think off..
But other shaders work excepts the ones packed in 2d toolkit. Is there anything im doing wrong ? I exported all my project assets then imported them in a new project and i get the same problem.
EDIT:
Seem like to do with scenes imported from Unity 4 or something i dunno. But if i create a new scene in Unity 5 and add a new tilemap based on existing data and tileset the shader work only for this scene once i paint tiles. But i also get tons of errors (total of 462).. The same error..
NullReferenceException: Object reference not set to an instance of an object
tk2dTileMapSceneGUI.DrawOutline () (at Assets/TK2DROOT/tk2dTileMap/Editor/tk2dTileMapSceneGUI.cs:253)
tk2dTileMapSceneGUI.OnSceneGUI () (at Assets/TK2DROOT/tk2dTileMap/Editor/tk2dTileMapSceneGUI.cs:440)
tk2dTileMapEditor.OnSceneGUI () (at Assets/TK2DROOT/tk2dTileMap/Editor/tk2dTileMapEditor.cs:1233)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
UnityEditor.SceneView.CallOnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1971)
UnityEditor.SceneView.HandleSelectionAndOnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1337)
UnityEditor.SceneView.OnGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1175)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)