Issues with Vive Stereo Rendering Toolkit

I've been wanting to try out the Vive Stereo Rendering Toolkit from the Unity Asset Store, but keep getting the errors below. This is with a fresh project running on Unity 5.4.4 as well as the SteamVR plugin, and after following the steps in this video.

If anyone has any thoughts they would be much appreciated!

 Assets/HTC.UnityPlugin/StereoRendering/Scripts/DeviceParamFactory/SteamVRParamFactory.cs(30,137): error CS0234: The type or namespace name `EGraphicsAPIConvention' does not exist in the namespace `Valve.VR'. Are you missing an assembly reference?
 
 Assets/HTC.UnityPlugin/StereoRendering/Scripts/DeviceParamFactory/SteamVRParamFactory.cs(30,65): error CS1501: No overload for method `GetProjectionMatrix' takes `4' arguments
 
 Assets/HTC.UnityPlugin/StereoRendering/Scripts/DeviceParamFactory/SteamVRParamFactory.cs(30,20): error CS1502: The best overloaded method match for `HTC.UnityPlugin.StereoRendering.SteamVRParamFactory.HMDMatrix4x4ToMatrix4x4(Valve.VR.HmdMatrix44_t)' has some invalid arguments
 
 Assets/HTC.UnityPlugin/StereoRendering/Scripts/DeviceParamFactory/SteamVRParamFactory.cs(30,20): error CS1503: Argument `#1' cannot convert `object' expression to type `Valve.VR.HmdMatrix44_t'