You need to reconnect the tags if the PLC model or address area has been changed.
If WinCC Runtime is showing #### in all fields, it could indicate that no connection has been established to PLC.
Try to Ping the IP address of the PLC, to ensure the physically connection to be OK.
Check under “Connections”, that only one connection has been created. Sometimes an extra is being generated by changing PLC.
However normally you only need one connection. And here you need to point out the right PLC in the column “Station”.
Check also that the IP Address is correct, below to the right.
Remember before the connection is available in WinCC Flexible, Hardware Configuration And NetPro needs to be updated, saved and compiled.
Check in the Tags list as show below, that the connection is the same as named under Connections:
Last click Options -> Reconnect… in order to synchronize all tags again.
If using a operating panel, check for correct IP address in “PG / PC Interface” under “Control Panel” in HMI device
If you are testing the HMI on a PC, please check your PG/PC interface settings as well. . (See also FAQ “Set PG/PC Interface”)