Hi @ROBERT_MOTTA,
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.
Just to verify, are you unable to connect to the QNAP Core on all remote devices?
Since experiencing this issue have you tried rebooting the QNAP and your networking hardware?
Thanks!