What is the Password to Unprotect the Gantt Excel Workbook?

We have protected the workbook in Version 4.0 and above to retain the digital signature.

You can unprotect the workbook by clicking the Settings button in the Gantt menu and then click the 'Unprotect workbook button in the project tab.

Please note that this unlocking the workbook may invalidate the digital signature. 
Nothing will be affected by the discarded signature. Everything will still work exactly as programmed. 
The digital signature has served its purpose — to give you confidence that the code was not tampered with in between the time that Gantt Excel signed it and when it was delivered to you."