Warning "This document contains invalid signatures" when opening an Excel file

Product
DocuSign Signature Appliance with Excel (2007, 2010, 2013 and 2016).

Symptoms
A digitally signed Excel file appears with an invalid signature warning.
This happens when the file is opened with an Excel version that differs from the one used during the signature process.

Cause
When Excel opens a workbook that was last recalculated in a different version (either a different product version or an update that introduces changes in the recalculation behavior), it updates the internal recalculation data to the actual version. As this data is part of the file content, the digital signature is then no longer valid because of this change in the content.

Resolution
Before signing, you need to switch the calculation mode to Manual.
To do this:
  • Select the "Formulas" tab
  • Click on the "Calculation Options" button
  • Select the "Manual" option

This setting is saved per workbook, but it can affect other workbooks that are opened in the same instance of Excel.
Note: Microsoft has confirmed that this is a problem in Excel 2016, Excel 2013, Excel 2010 and Excel 2007.
 
Workaround
There is an additional option that will prevent the issue, but it is not recommended, as it will impact all workbooks opened in Excel that were last saved in an earlier version (whether or not they are digitally signed).

Disabling this full internal recalculation behavior with a registry key is possible. The registry key was implemented for testing purposes and is not documented by Microsoft. It is not intended for customer use and is not recommended by Microsoft. It could also result in further issues with calculation anomalies between the workbook calculation chain and the new calculation engine which have not been tested for. If this registry key is used, there is no guarantee that calculations are accurate or correct.

Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Excel\Options 
Add new DWORD value: FullCalcOnLoadOldFile 
Set value to 0
(16.0 is for Excel 2016, for Excel 2013 use 15.0 and Excel 2010 it would be 14.0)

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Thank you,
The Signature Appliance Group at DocuSign Support