TPTAPI does not write out to a file. That is up to your application.
Thus, if your file is empty, you will have to debug your application.
The data that will be provided from a call to GetRow is in binary format.
If you want to write the data out in csv form, you will have to convert the data to character and add the delimiter.
The data is provided in indicator mode and so you will also need to process the indicator bytes so that you know which fields need to be NULLed.
You may want to add some diagnostics to output the data length after the call to GetRow to make sure you are actually getting data.