I believe that many things about EOS and OnlineSubsystem are deprecated.
I’ve tried a lot of things. For example EOSPlus, OnlineSubsystemEOS no longer work.
I think they are simplifying things. Because there was a lot of confusion. Many variants to do the same… a complete disaster. The documentation is outdated.
I have read that they have already released the second version OSSv2. You can see it is already in the plugins.
Steam uses links to invite friends and Epic uses the UI button. So I don’t think they’re going to get that synchronized in any way.
Ok, they warned that plugin is experimental. So it is understandable that many things do not work.
The incredible thing is that the pugin has been experimental at least since 2016. So I really don’t know what to think about it.
It’s absurd to make a multiplayer game if you don’t have a reliable tool that allows you to connect to the platform.
At least you can create sessions, save achievements and statistics on the epic side. The only thing that doesn’t work is inviting friends.
Anyway, less gives a stone 
Thanks for answering.
Regards!!