Unity Player Settings for Vuforia projects can be a source of problems if incompatible platform settings are selected. The Player Settings layouts changed a bit between Unity 4.6.x and Unity 5.x. Here's some comparison screenshots of the Vuforia-compatible Unity Player Settings for iOS and Android in Unity 4.6.x and Unity 5.x to verify your project settings against.
Key Settings for Vuforia Unity Projects:
- Make sure OpenGL ES 2.0 is explicity selected. Turn off Automatic for Graphics API. Vuforia doesn't support iOS Metal or OpenGL ES 3.0.
- On Android, make sure to use ARMv7. A device may have an Intel chip, but Vuforia needs to be compiled with ARMv7 and the device can attempt to use ARM emulation to run it.
- If you're using "Stripping Level" and experiencing crashes, then set it to "Disabled".
- For iOS, use IL2CPP for the Scripting Backend. Mono (2.x) is 32-bit only.
- Use "Forward" for the Rendering Path.