The Programmer's Toolbox code is public and installed into you CVI folder, you can find it in <CVI folder>\toolslib\toolbox. By looking at the code you can easily understand the reason of the error message (e.g. an incorrect parameter value or other reasons).
You can even run the Toolbox in the IDE to debug this condition: load the instrument in Instrument menu, next run Instrument >> Edit... menu function, select the PT in the list of instruments included in the project and press Attach and Edit Source button: the code will be loaded into an editor window and you will be able to run your project adding breakpoints into the instrument code and examine variable values and/or run step-by-step to investigate.
