Voted best answer
If you are using a PM554 it only has 1 com port, Except if you have bought an extra.
Your com1 is defined as modbus rtu for communication to the cpxxx panel.
That gives you the log on problem.
If you set the plc in stop and do a power cycle you will be able to connect again.
You have to set the parameter enable login in the modbus rtu configuration and use the same login parameters as you communiction with the panel. Baud rate, parity etc.