IP address change on a PM556 ETH
IMHO you use one wrong mode of change the IP adress.
In Automation Builder tool (but in Control Builder is the same) you need to select
Tools --> IP configuration SCAN button.
When scanning detect your CPU, you can read the actual IP adress. In the bottom side of your screen you can modify and send to the CPU the new IP adress. Please sure that the CPU is in stop mode. After the sending, with one new scan you can verify if the new IP adress is correct stored in the CPU.
Please note that during the operation, usually the PC and the CPU must have the same web domain.
In my cpu this procedure always works fine.
Hope this help you