Office 365 Copilot error creating new Excel Workbook

From your message, I did not see you required any reply. I have reported using the link you supplied as best I can.

The versions of Microsoft 365 Copilot I have installed are. 18.2502.1041.0 and 18.2501.1284.0 But both give the error: "Excel cannot open the file 'Book 2.xisx because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file." when it opens the installed version of excel

UPDATE:

I have a second Desktop PC, which exhibits the same symptoms.

I have reset the Microsoft 365 Copilot app and followed all your suggestions on that machine.

My Conclusion is that the problem is with Microsoft the Application, not my PC's. The Excel New Workbook Button Does NOT function correctly in Microsoft 365 CoPilot Front End.

Hi Colin

Thank you for your reply and trying the above.

Based on your feedback, indeed, you are still exhibiting the same symptoms using other computers, this is most likely a temporary issue with Microsoft 365 Copilot, you can double check if Microsoft 365 Copilot is the same version on both computers, alternatively, you can feed the issue back to the developer community, there will be professionals over there to The issue will be noticed and fixed in a later version. Until then, you can create a table using Excel as a temporary solution.

Microsoft 365 Copilot app​ · Community

Finally, thanks again for your reply, it's a great find and he'll help us identify the problem and help more users.

Have a good day!

Best regards

Adrian.C-MSFT | Microsoft Community Support Specialist

Adrian.C thanks, I have tried all the steps above without any success.

The problem only exists when I try a new file from the MS 365 CoPilot window as shown below. When I chose create new, workbook excel. If I do new workbook from within the excel all via file new, all is OK. It creates Book.xlsx then Book 1.xlsx and so on and results in the error. The left over files are 0KB in size and I have to delete them from my OneDrive Personal Folder.

Hi Colin Dowse1

Welcome to Microsoft Community.

I realize that you've encountered a problem with " Office 365 Copilot error creating new Excel Workbook ", and I understand how you feel. Don't worry, I'll do my best to help you.

Regarding the "Excel cannot open the file because the file format or file extension is not valid" error message, this issue may be related to several factors. Here are some possible solutions:

Check File Extension:

• If you encounter this error while trying to create a new spreadsheet using Microsoft 365 Copilot, first check the file extension. Ensure the file extension is .xlsx or .xls, and not any incompatible formats.

Clear Temporary Files:

• Excel and Office 365 Copilot may create temporary files when generating files. If these temporary files are corrupted, it might prevent the creation of new workbooks. Try clearing Excel's temporary files:
  • Press Win + R to open the Run dialog, type %temp%, and press Enter.
  • Delete all temporary files in the opened folder.
  • Then restart Excel and see if it resolves the issue.

Update Microsoft 365 and Excel:

• Ensure your Microsoft 365 and Excel versions are up-to-date. Sometimes, program errors are fixed with updates.
  • Open any Office application (like Word or Excel), then click "File" in the upper-left corner.
  • Select "Account", then click "Update Options" > "Update Now".

Disable Add-ins:

• Some Excel add-ins might interfere with the file creation process. Try disabling all add-ins and retrying:
  • Open Excel, click "File" > "Options" > "Add-ins".
  • At the bottom, select "Manage" > "Excel Add-ins", then click "Go".
  • Disable all add-ins and restart Excel.

Use Office Repair Tool:

• Office provides a built-in repair tool to fix potential issues:
  • Open "Control Panel" > "Programs" > "Programs and Features".
  • Find Microsoft Office, right-click it, and select "Change".
  • Choose "Quick Repair" or "Online Repair" and follow the prompts.

Clear User Profile:

• If the above methods do not work, the issue may be related to Excel's user profile. Try resetting the profile:
  • Close all Office applications.
  • In File Explorer, navigate to %appdata%\Microsoft\Excel.
  • Delete or rename the folder (this will reset Excel configuration but won't delete files).
  • Reopen Excel to see if the issue is resolved.

Try Different Creation Methods:

• Try creating new workbooks through other means, such as through Excel's menu or manually using Copilot to create other types of files, to determine if the issue is specific to Copilot or Excel itself.

Feel free to share updates with me on how things are progressing after you've completed the aforementioned steps. Should you have any questions or require clarification, do not hesitate to reach out to me. I‘d like to do my utmost to assist you.

Best regards

Adrian.C-MSFT | Microsoft Community Support Specialist