Hi @KnockKnock,
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.
Do you have any active antivirus or firewall on the Core machine? If so can you try disabling temporarily and let us know if there is any change here?