Text encoding for your Project CSV file needs to be UTF-8. This is typically the default choice for most spreadsheet programs — but not always. If you're prompted to select a format when using your spreadsheet program, be sure it's UTF-8. If you receive this error, check your spreadsheet program an ensure that you're saving to the proper format.
If you continue to have problems, try copying and pasting the contents into a new spreadsheet. If that doesn't resolve it, try using Google Sheets and saving as a CSV to your desktop.
For bom|utf-8 format errors...
"File error: "File is not proper CSV format (0) - unknown encoding name - bom|utf-8 [bom|utf-8:utf-8]"
There are a couple ways to correct this:
Windows, by way of Notepad++
Retry the upload. If problem persists, another bom issue exists in the data itself. Look for characters obviously out of place and delete them.
TextEdit in Mac OS seems to have a similar thing. Another Mac option is re-saving via Numbers.