If you cannot open an Excel file and see Excel cannot open the file because the file format or extension is not valid error, see this post.

If Excel Online is not working and you see errors Couldn't Open the Workbook, or Request Was Taking Too Long, then see this post for the fix.

However, if I load the Excel first, all Excel files could be accessed or displayed without any trouble. The problem makes it very inconvenient to search for a file and load it immediately.

Q. When I open Excel, I always have to choose Blank workbook. Is there any way to have Excel do this automatically and skip the step of getting the Start screen? Q. I have a folder of Excel files that ...

Numbers has the ability to open Excel files so you can work on them. You can also export spreadsheets in Numbers so that they are compatible with Excel.