How to Fix Excel File Extension or Corruption Errors from SharePoint

Reach out to your organization's IT department if you do not have Microsoft 365 administrative privileges.

Have the administrator sign in to the Microsoft 365 admin center using their credentials.

Click on the 'Support' section in the left-hand navigation menu, then select 'Help & support' or 'New service request'.

Provide details about the SharePoint Excel extension error, noting that it affects multiple users, and request that the Microsoft team collect diagnostic logs for investigation.

Open your preferred web browser and log in to the SharePoint site containing the problematic file.

Navigate to the specific document library and folder where the newly created workbook is stored.

Click the file name directly. This forces the workbook to open in Excel for the Web, which often bypasses desktop-specific extension validation errors.

Determine if you are accessing the workbook via a copied sharing link or directly through the SharePoint directory.

If using a sharing link, ask the file owner to grant you direct access at the file or folder level instead.

Go directly to the SharePoint document library URL and attempt to open the file from there to rule out corrupted sharing links.