Video is normal after installation and wiring, but Ethernet or voice services are not working. How should I troubleshoot?

Troubleshooting should be performed in order from the optical path to the ports. First, confirm that the fiber pair is correctly transmitting and receiving at both ends, that there is no break in the optical path, and that the panel status indicator lights show no anomalies after the device is powered on. Then verify that the service interfaces on the transmitting and receiving sides correspond one-to-one, that the two Ethernet groups are not crossed, and that two networks requiring physical isolation must be connected to their respective channels. Next, check whether the RJ45 connectors and wire sequence of the network cables are properly made, and whether the telephone line terminals are securely connected. If video service is normal but only one channel is not working, it usually indicates that the optical path is normal, and the problem is mostly in the interface, cable, or port status of the remote device for that service. If video images show interference or flickering, check the shielding and grounding of the video cable and whether the connectors are loose. If the issue still cannot be resolved, it is recommended to contact the manufacturer's technical support with the device alarm information.