Windows 11 Update on 24/07 and now I can't open any excel files, these were all working previously

Copper Contributor

Hi guys,


Hoping you can help me.


All the files were working completely fine yesterday, until after I ran the Windows update last night. Today, none of the files I need will open, I'm getting the same error message for everything.


"Excel cannot open the file 'XXXXX' .xlsx 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"


I've tried multiple troubleshooting processes; permissions, previous version, DDE, all sorts. Nothing is working.

This is clearly linked to the update rather than the files themselves, does anyone know if the latest update has caused Excel files issues and if so, how do I fix?



3 Replies


Can you open such file from File->Open after the running Excel app?


Strange. Even if you create new workbook, save it and try to open from another Excel?

If so I'd try to  Repair an Office application - Microsoft Support