This has to do with the settings on your computer. The following guide is for Mac users only:
Here's a way to force any app to open any document:
- Make sure your Dock is visible.
- Select your .csv file in the Finder.
- Grab it with your mouse and move it over the Excel icon in the Dock. Do not release the mouse button.
- Hold the Command and the Alt key on your keyboard.
- Release the mouse button.
Another option is to set Excel as the default program to open CSV at all times:
- Right-click on a CSV file
- Click on Get Info in the pop-up.
- Click Open With if the section isn't already expanded.
- Click the dropdown and choose an app.
- Click Change All...
- Click Continue when the Finder asks you if you're sure.
Now any time you open a file with that extension, the Finder will automatically open it with the app you've selected.