"This document contains invalid signatures" error when opening Excel workbooks that were digitally signed in an earlier version
Office 365 ProPlus is being renamed to Microsoft 365 Apps for enterprise. For more information about this change, read this blog post.
You open a Microsoft Excel workbook that was digitally signed in an earlier version of Excel than the one that you are using. In this situation, the signature is no longer valid, and the following warning message is displayed in the Trust Bar:
This document contains invalid signatures. [View Signatures]
When you open the digitally signed workbook in same program version that it was created in, the workbook opens as expected without an error message.
When Excel opens a workbook that was last recalculated in a different version (either a different product version or an update that introduced changes in the recalculation behavior), it updates the internal recalculation data to the current version. Because this data is part of the file content, the digital signature is no longer valid because of this change in the content.
Before you sign the workbook, switch the calculation mode to Manual. To do this, select the Formulas tab on the ribbon, and then select Manual on the Calculation Options list.
Although the calculation option is saved per workbook, it can affect the setting for other workbooks that are opened in the same instance of Excel.
If the workbook is already signed, follow these steps:
- Before you open the workbook, start Excel through the Start menu.
- Change the calculation mode to Manual. To do this, select the Formulas tab on the ribbon, and then select Manual on the Calculation Options list.
- To open the signed file, select Open on the File menu.
The signature should be displayed as valid.
If the calculation in any workbook is made when the workbook is open, the signatures will be invalidated because they are updated even if they return the same value.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.