For anyone else having this issue, I was able to get this working by bypassing the “is HMD Enabled” check in the BP_VRSpecatorCamera_Base class in the Enable Spectator Screen function. I tried enabling HMD in the blueprints beforehand, but that didn’t seem to work. My guess is my machine/app was too slow connecting the HMD because this worked fine in the editor.
Obviously this skips a useful check for debugging, so I’m planning on finding some other way to implement this to check if an HMD is attached. Potentially something with the *Is Head Mounted Display Connected *call.