Dedicated Server Session in Steam not findable

So I compiled my project from an unreal source build into a dedicated server. The Project is using the Steam OnlineSubsystem.

The Server seems to start correctly

https://forums.unrealengine.com/filedata/fetch?filedataid=124407&type=thumb

This is the RegisterServer function overridden by me to register the session in the online subsystem

https://forums.unrealengine.com/filedata/fetch?filedataid=124408&type=thumb

So then i have a client with a UMG button calling a c++ function that inside of my game instance fires following “FindSessesion”:
(It’s being called from an own c++ UBlueprintFunctionLibrary that provides a “FindDedicatedServerSession” BlueprintCallable, see 4th picture)

https://forums.unrealengine.com/filedata/fetch?filedataid=124409&type=thumb

But no matter what I do I can’t get my Client to find the dedicated server’s session. how can I figure out why it’s not being found? What could go wrong here? Hopefully, someone can help me here, i sooo need to get this to work and I’ve been working on this for some time now. I have already reached out to Discord and Reddit but got nowhere so far.

Looking forward to your responses, thanks, guys.