Spreadsheet Compare no longer is able to save results to exported Excel file

Hello @Mokusch, Silvia

Welcome to the Microsoft Q&A Community! 

Thank you for contacting us regarding the issue with exporting results from Spreadsheet Compare to an Excel file. I understand that you are receiving an error message indicating that the workbook could not be opened when attempting to save the export file.  

To make sure we're aligned and avoid from any misunderstanding, please let me know a few details about your issue by answering these questions: 

1. As I see you used the tag "for Business", may I have your reconfirmation if you are signed in with a personal account (e.g., @hotmail.com, @outlook.com), an education account (e.g., @school.edu), or a work account (e.g., @yourcompany.com)?  
2. Does the error occur with all comparison operations or only with specific workbooks? 
3. Have you tested exporting to different file locations, such as a local folder under your user profile (for example, C:\Users<username>\Documents)? 
4. Are you running Spreadsheet Compare with standard user permissions or as an administrator? 
5. Is the target folder located on a local drive, a network share, or a cloud-synced location such as OneDrive or SharePoint? 
6. Can you manually create and open a blank Excel workbook in the same folder where you attempted the export? 
7. Did this issue begin after a recent Office update or Windows update? 
8. Are there any group policies or security settings in place that could restrict file creation or application interaction? 
9. You mentioned that both Microsoft Report Viewer 2015 Runtime and Microsoft Report Viewer 2008 are installed. Have any changes been made to these components recently? 

In the meantime, I recommend you try the following steps and let me know the results. 

Run Spreadsheet Compare as Administrator 

Launch Spreadsheet Compare with elevated permissions by right-clicking the application and selecting “Run as Administrator.” This will help determine if the issue is related to file access permissions. 

Verify Excel File Association and Functionality 

Confirm that .xlsx files are associated with Microsoft Excel. Additionally, create and save a blank workbook in the target folder to ensure Excel can access and modify files in that location. 

Remove Legacy Report Viewer Components 

Uninstall Microsoft Report Viewer 2008 (KB971119) as it may conflict with newer Office components. Retain Microsoft Report Viewer 2015 Runtime and repair it if necessary. Ensure that SQL CLR Types prerequisites are installed. 

Repair Microsoft Office Installation  

In case you're using Windows 10 or 11, try repairing the office app via Repair an Office application - Microsoft Support   

If none of the above steps resolve the issue, consider updating to the next Semi-Annual Enterprise Channel build or rolling back to the previous build to rule out a regression introduced in the current version. 

Once I receive your responses, I can provide further supporting steps. Thank you for your cooperation. 

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".  

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Hello Q&A Team,

I'm posting this under my work account ID

I had already checked all your questions from 2-6 when I posted my question. So:

2. all workbooks - same error
3. all target folders - same error
4. with elevated rights - same error
5. no, only local or file share, not oneDrive or Sharepoint
6. yes, no issues with basic Excel functions

It must have started after last feature update, but I have to verify.
We have Trellix in place that could interfere with excel trying to save - as virus-scanning is always a possible cause. (but I cannot disable that)
I don't know of any group policies that might block file saving.

About ReportViewer - we have that in place after we had run into a similar issue with "Database Compare" But I will also test if removing will have an impact on the issue.
I'm looking for an option where to find what is causing the issue. I.e. will I see anything in event viewer? I haven't found anything so far.