I couldn't find any information about the design problem in Forte Embroidery Suite. You're probably doing something different or wrong as opposed to what's been defined in the user guide/manual of the application.
I recommend you access the file to see what is the correct procedure to center a design in Forte Embroidery Suite. The user guide is in PDF format and on page 11 (inside the file) you'll find all the instructions regarding the center part.
Note: The PDF is stored in the archive available for download from the developer's website.