Modbus TCP App issue.

Hello Community,

I am new to Modbus TCP App,

I am using S20-ETH-BK and S20-DIDO-8/1,

I am testing ctrlX Modbus TCP App to write to digital output, but however the digital output LED indicator did not light up.

Below is my setup.

Plug & play is disabled.

Designation "D" is flashing green - 

ctrlX Modbus TCP App setup

I am unsure if it is because my S20-DIDO-8/1 designation "D" is flashing green or my setup is incorrect. 

Hope someone can advise me.

Warmest regards,