When you configure XLS Padlock to protect your formulas, the software has two methods to do so. Either it modifies formulas directly in the source file of your workbook (this is the recommended method that works in the vast majority of cases). Either it controls Excel by automation.


If the recommended method fails, you can force XLS Padlock to use the method by automation: to do so, enable “Use Excel automation for formula protection”. The latter will be automatically chosen if you protect a workbook in binary format (XLSB) or very large.

You can also consider to activate "Ignore errors when processing the workbook (internal protection)" but, in that case, be sure to test your compiled workbook.