Ok after some struggling, i got it working in 4.21.
Before i used the VOIPTalker i was using the default voice so i tested if it works without calling PlayerController->StartTalking() and in result it seems that its not required for spatial voice.
All you need to do is, to add the VOIPTalker component to your Character and Multicast the Voice Init as described before.
VOIP seems to not work in PIE Sessions so run your game as standalone
when it runs on server and not on client, it should tell you all.
check your replication check if you are on server, and if so, then perform a multicast of the voice init
Edit:
I want to mention, that it runs perfectly over Steam and also with Subsystem NULL, just checkout the config settings in the posts before, thank you guys for working out this thread and providing these informations!
Awesome job for this update and the spatial voice implementation just epic…, as always.
Epic - I love you so much <3
You make me feel like a christmas child every single day