Using 6 cameras. NVR is plugged into UPS. Office secretary came to work on Monday. No power outages over the weekend. No Link is displayed on the Monitor for all 6 cameras. POR the Hikvision, link LEDs blink trying to connect/detect and then go dark. Unplugged power cable tried again. Try to connect/detect and go dark. We have had this problem on/off for a year. The cameras had always come back on and displayed after a POR. I haven't checked voltage for the Poe. Since the LED's blink at the startup, I thought the power supply was OK.