Before we conducted the troubleshooting we check the monitor first and asses which camera has problem.
After assessing the problem we checked the connectors and Ethernet switches. From end to end we connect the LAN cable tester to check if the LAN cable is still have connection. In this case we concluded that soft RJ45 connectors are worn our so we crimped another RJ45 connector on the line cable. The other cable is not working so, we laid another LAN cable.
After crimping and laying another LAN cable we connect all connectors. after connecting all unplugged RJ45 connectors just wait for few minutes at it will work. In our case we troubleshoot it successfully.