VR not work on 5.1.1f1

I update 5.1.1f1 yesterday, and get the message “Failed to load ‘C:/Program Files/Unity/Editor/Data/VR/OVRPlugin.dll’ with error” when i click VR support in playersetting.

5.1.1 has major OVR upgrades.
Check release notes.

For your project backward compatibility, uninstall OVR asset and reinstall the latest version.
If you have issues with VR, uncheck the stereovision option in Player settings (I don’t remember the name)