What there SDK for UE4 actully looks like? can you paste image what it contains? look on there “documentation” looks like insted of implementing it as OnlineSubsystem they did some client actor, which is not how you suppose to implement online service in UE4… but that might be the cause of lack of documentaion for OnlineSubsystem system
Also i think you will get better help thru there support, because it’s there product not Epic’s