VR Preview Not Displaying in Headsest

Hi, I am working on a virtual reality UE5 project using a Varjo XR-3 as my headset. The VR Preview is showing what I create perfectly, including tracking both the headset and my hands (I am using the Ultraleap Tracking Plugin & the VarjoOpenXR plugin), but the headset is no longer displaying the project upon running it. The headset just displays the real life environment around me. I have tried enabling and disabling various plugins (Oculus etc.) as suggested on other forums. The headset displays as normal using other software so the issue is on UE5. The headset does not display on any project I create, not just the one I am working on at the moment.

To clarify, VR Preview shows what I would expect while the headset shows nothing.

Has anyone encountered a similar issue? And if so what did you do to overcome it?
Thanks