It sounds like it is a binary Excel file then that has been mislabeled. It pretty much says what this has all lead back to with ‘the file format and extension of attrition.csv don’t match. The file could be unsafe or corrupt’.
Please go back and read the first link I provided , Getting good answers to your questions , because I am left here scratching my head that you had this information all along and thought not to share it?
Anyway…
So after you open it, save/export it as an actual comma-separated file from Excel and you should be able to use the text based file anywhere. It should then open in Notepad, that you mention, as text. (Hopefully you meant Notepad++, and not Microsoft Notepad. Anything Microsoft has, except finally VSCode, opens & saves with special things that will cause you headaches when you try to work with them in Python. You’ll be confused. Please use a proper code editor, if you aren’t already.)