Thanks for reaching out, @Sven_Olof_Ersmarker!
So we can better assist you, please provide a brief description of your current setup using this link as a guide.
Make sure to describe your network configuration/topology, including any networking hardware currently in use, so we can have a clear understanding of how your devices are communicating.
If it’s enabled, can you try temporarily disabling any firewall on the Core machine? Once you do this is there any change?
Are other endpoints being found by Roon?
Thanks!