Error while running the service

I have created a flow service which converts a flat file into values by calling the service convertToValues in WMFlatFile.
After converting other business logics are written.

The problem is that when I trace the service it runs well but when I run it ,the service throws error saying that ffData cannot be null.

I checked my service and found that valid value is mapped to ffData of convertToValues.

If anyone knows the reason then please let me know the cause and solution.

It means while runtime, the input to this ffData is null. Save the pipeline and debug the service. Check for typo errors in parameter names.