Cannot open file because the file format or file extension is not valid.

Question

We're getting this error {Cannot open file because the file format or file extension is not valid.} on one of our macs with office 365 (current MacOS and Office). 

When the file is opened on another system there is not problem.

I trashed the plst for all the microsoft products in the lib/prefs but it didn't solve the problem.

Answer 1

First, go to the Excel menu and choose About Excel. Make sure the version is either 16.13.1 or 16.14.  If it is not, install updates:

Ensure your Mac and Office have the latest updates. Here’s how to install updates:

Make sure your Mac has a working internet connection, then:

1. Update Mac OS X. Open the App store and click on the Updates button. Install the updates.
2. After, in any Office application go to the Help menu and choose Check for Updates to launch the AutoUpdate app. Let AutoUpdate install updates and then restart your Mac.

If you use Antidote, Webex, Silverlight, EndNote, Zotero or other add-ins there is a potential for crashes unless you also update your add-ins to the latest update. Install updates for these programs if you have them.

If updating office wasn't necessary or doesn't fix this problem, the next area to check into is the file path. Make sure your startup volume has a name that does not contain anything other than letters and numbers. Same thing for all enclosing folders, the workbook's file name, and sheet tab names. Avoid special characters as well as the word History. Also, make sure the workbook's name isn't really long and that the entire file path isn't super long.

Answer 2

Hi ODTN,

Thanks for posting on our forum.

According to the error message, I suggest you change the file to another format, such as .xls to .xlsx.

If the issue still exists, could you please provide the following information?

1. Check if all files meet the issue.
2. The affect files’ format, and the file name as we need to confirm if it includes a special character
3. The OS version and Office version. (Click Excel>select About Excel)
4. In which version of Office did you create the affected workbooks?

Thanks,

Qing

Answer 3

Hi ODTN,

Did the issue still exist? Do you have any updates?

Thanks,

Qing