If I click on an invite in the Oculus windows application, the InviteResult passed to my delegate from FOnlineSessionOculus::OnRoomInviteAccepted is asserting as !IsValid when I try to pass it to JoinSession.
Note that if I have the game running and then accept the invite in Oculus Home, everything proceeds correctly (no assert).
Definitely sounds like a bug and we will look into this. Is the FOnlineSessionSearchResult itself invalid? Or is there no OwningUserId for the session or no SessionInfo?