Excel typically saves a csv file as ANSI encoding instead of utf8.
One option to correct the file is to use Notepad or Notepad++:
- Open the .csv with Notepad or Notepad++.
- Copy the contents to your computer clipboard.
- Delete the contents from the file.
- Change the encoding of the file to utf8.
- Paste the contents back from the clipboard.
- Save the file.