Problem with p-files execution

Hello Community,

I downloaded some well-known MATLAB toolbox from the link below:

https://github.com/ElsevierSoftwareX/SOFTX-D-17-00059

The main file is tfsa7. I initialize a GUI without any problems, by calling tfsa7 in command line and I can normally interact with this GUI. However, after clicking pushbutton which calls some p-file function, I get the following error:

Attempt to execute SCRIPT gsig as a function:
C:\path\TFSAP_source_Dec_2016\gui_m\gsig.p

Please help solving me this issue.