Valve's SteamVR Input Plugin

Has anybody encountered a problem where the plugin wont work in a packaged build?
I have set up all the input actions inside UE4s project settings and added the actions in to my blueprints.
Everything works fine in VR preview and people are telling me that it works in the Steam beta but, for some reason I just have no buttons working on my dev machine when I download my game through steam.

Strangely though the sample bindings do work in the packaged build, just none of the custom bindings.
This is also the case if I launch the packaged build locally instead of the version downloaded through steam.

If anybody knows what might be causing this please help. Ive wasted a week on this now and my game is due for release in 5 days time.

Thanks, D