Invalid Process Parameter

I am getting an Invalid Process Parameter error in my interface, and i made sure that the parameters have the same name and type in both process model and Interface.

what might be the reason of this error ? 

a!startProcess(
                                processModel: cons!GeneratePDF,
                                processParameters: {
                                customerNum:ri!customerNum,
                                descriptionReason:ri!reqDetails.reasonDesc,
                                data:ri!DocDetails,
                                },
                                onSuccess: {a!save(
                                  local!pdfId,
                                  fv!processInfo.pv.CreatedPDF
                                )}
                              ),