GT Designer requires a 12-digit typically found on the License Certificate included with the DVD or digital purchase.

Ensure you are using the latest version of the MELSOFT Update Manager . Sometimes a Windows update breaks the license service, and a software patch from Mitsubishi is required to fix it.

If you are comfortable with command-line tools, use the MELSOFT diagnostic tool.

: Look for folders named "GT Designer," "GT Works," or "GT Title" (common in some software variants). Rename or Delete

Ensure you are using the correct version of GT Designer for your hardware. For example, projects require GT Designer3 Version 1.100E or later. If you're using an older version, the software may not recognize the license for that specific hardware series. Re-initialize Library/AppData (If error persists) :