Function blocks in Ladder Logic (LD) need to be enabled.
In the Codesys toolbar, use the Box with EN option to insert a function block. This will default as an AND block. Highlight the AND function and press F2 for the input assistant or type C3_Input or C3_Output. As with ladder programming, inputs are read first, program is executed and outputs are set before the next cycle, the input block should be set on the first network/rung of the program and the output block the last.
