PLC Running But HMI shows communication Error- How will You troubleshoot?

In a production plant, a machine suddenly stops working. The PLC CPU is in RUN mode, but the HMI displays: "Communication Error – PLC Not Responding" The Ethernet cable connection looks normal.

As an automation engineer, what will be your troubleshooting approach? Discuss the possible reasons: PLC IP address mismatch Duplicate IP address in the network Communication driver configuration issue Ethernet switch failure Cable or connector problem PLC communication module fault HMI project communication settings

What will you check first before restarting the PLC or stopping production? Share your real troubleshooting experience.