CIL Generator Error (CILG0016): The conversion of '...' values to data type '...' is not supported.

The CIL Generator has detected a data type conversion which is not supported.
The error message has been generated because you have connected a data type to an overloaded type converter function which is not supported by that function (due to a non-matching size of In and Out data type).
The help chapter "Data Type Conversion" (IEC 61131-3 Functions and Function Blocks help) specifies the allowed data types at the input of each overloaded converter function.

Error example in FBD

A REAL data type is connected to the input of the TO_LWORD function.

Remedy
Double-click the error message to jump to the affected code position.

Adapt the data type of the variable connected to the converter input.
If exactly this data type of the variable at the function input is needed, use a suitable converter function that is upstream of the converter mentioned in this error.