I have a DS-7616 NVR that I've been running for over a year. Several cameras on it. No changes have been made in weeks, if not longer. Today, with monitor on, all camera views disappeared, with error, Network is unreachable. Cameras are connected via ethernet to separate POE switch. I have checked settings, rebooted NVR, to no avail. I can pull SADP up and see cameras are there, I can log into cameras via web browser and see views. I have changed ethernet cables to NVR and tried different ports on switch. No joy. What else can I check? Settings, ie, ip address etc are the same as before and appear correct. thanks