I think you might have to include a little bit of logic to orient the HMD and Camera correctly at the start of the game.
In the demo project we put together found in our VR Demo, such behaviour has been implemented (as well as a way to scale your player to their in-game avatar so that motions map accurately). The relevant nodes are the ‘Set Tracking Origin’ and ‘Reset orientation and position’ shown in the attached picture for getting the HMD and camera (‘FRCamera’ in the example) to align which are triggered during a calibration routine.
