I think you may need to define a TABLES parameter into which the results of the function call will go.
This function returns the results in a tables parameter named LINES.
I'm not sure which technology you are using here, but a few years ago the DCOM RFC connector required me to call fc.DimAs("LINES") to return a table object which would contain the results of the function call. The call to DimAs needed to come before the function was executed.
This may be the missing parameter referred to in the error message.