Office 2021: Excel: In just last few days my main Excel files will not open

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Hello John Mitchell!

From what you shared, I understand Excel files in a specific folder that used to work are now unable to open, while files in other locations are still fine. This suggests the issue may be related to that folder or how Excel is accessing files from it, rather than a general Excel problem.

First, it’s worth checking for a path/name issue rather than the files themselves. Excel can fail to open workbooks if the full folder path or filename gets too long, so try renaming the parent folder (and any subfolders) to something short (e.g., C:\Excel) and shorten one file name (avoid using special characters), then test again.

Q&A Assist’s Open and Repair is a good first test on a single file (it targets the workbook). If that doesn’t help across multiple files, repair the Office installation instead:

• Start > Installed apps / Apps & features > Microsoft 365/Office > Modify > Quick Repair.
• If Quick Repair doesn’t help, move to Online Repair using the same steps (choose Online Repair), then restart and test again.

As a workaround, try uploading the file to OneDrive and opening it from there (or choose Open in App). This lets Excel access the file via the cloud location instead of the local synced path, which can sometimes avoid path or permission limitations.

Additional step: Check McAfee > Navigation > Quarantined and Trusted Items > Quarantined Items, and restore any Excel files only if you recognize and trust them (sometimes antivirus may block or isolate valid files).

Hope one of these helps. If not, feel free to post back, I'm happy to support further!

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The error indicates that the workbook files in that specific directory either no longer match the .xlsx format or have become corrupted.

Based on the available information, the following supported actions can be taken:

1. Verify the file extension and format
   • Confirm that the affected files truly are Excel workbooks and not another type of file renamed with .xlsx.
   • If the files were inadvertently renamed, open them in Excel and then save them in the correct format with the appropriate extension.
2. Consider file corruption and attempt repair
   • The message can appear when a workbook is unreadable or corrupted and its contents no longer resemble the expected Excel format.
   • Use Excel’s repair capability:
     1. Open Excel.
     2. Select File > Open > Browse and navigate to the folder containing the affected file.
     3. Select the file once.
     4. Use the drop-down arrow next to Open and choose Open and Repair.
     5. If prompted, choose Repair to try to recover as much of the workbook as possible.
3. If the file came via email
   • If any of the affected workbooks were received as email attachments, save the attachment to the local drive first and then open it from Excel (rather than opening directly from the email program).
   • If the sender is trusted and the file still will not open, ask the sender to resend the workbook in Excel Binary Workbook (*.xlsb) or Excel 97-2003 Workbook (*.xls) format.
4. Evaluate the folder and storage
   • Because only files in one directory are affected, check whether anything changed about that folder or its storage (for example, moved from one drive to another, copied from a USB device, or restored from backup).
   • If the files were on removable media or an external drive, ensure the device is healthy and that it was not disconnected while files were open, as this can cause corruption.

If the files remain unreadable after using Open and Repair, this indicates corruption beyond what Excel can recover. In that case, restoring from a backup (if available) is the only supported recovery path.

References:

• A file is in a different format than its extension indicates in Excel
• Open a document after a file corruption error