After we install new LCD driver for HMI Viewer, we get the communication not properly so we can't monitor GTG Mark V control from viewer. Cimplicity (unit_T1) was loaded but no parameter displayed (#######).

 

If the only thing done was to install a new driver on the CPU being used for the HMI Viewer for an LCD monitor, that should not have affected CIMPLICITY's connection to the HMI Server. That's done over an Ethernet connection, usually referred to as the PDH (Plant Data Highway).

Have you confirmed that the Server and Viewer can ping each other over the Ethernet network?

Did you do any MS-Windows updates on the HMI Viewer while installing the LCD driver?

Have you shut down and restarted the HMI Viewer? The HMI Server?

Did the new LCD driver significantly improve the data and graphics seen on the monitor?

Based on the information provided, this is likely not a CIMPLICITY problem.