There is no obvious issue. Highlight execution or use data probes to ensure you actually have data. This may be your root issue.
As a side note, you have almost done all the work the write to spreadsheet string does. I would recommend going all the way and replacing the write to spreadsheet with direct calls to the file I/O primitives. You will need to add separators between your fields. Open the write to spreadsheet string to get what you need to do. I would recommend you not use anything not on the palettes, and there are some subVIs in that code which qualify. Or, don't convert to strings, use the DBLs and let the write to spreadsheet format it.
You also do not need to index out the waveforms in your first loop to scale them. You can do that on the array of waveforms directly.
What error do you get when you try to post your code? You should be able to do it.
