The rules for importing are simple:
Make sure your file type is a .CSV file (not .txt, .xlsx, etc.).
MSKU, Cost/Unit, and Purchased Date are must-haves. If you leave the other columns blank, that is okay — headers need to stay, though.
Prices cannot have a $ in them.
Dates must be in MM/DD/YY or MM/DD/YYYY format.
Headings should not have any commas. As a comma-separated import, it will separate incorrectly.
The file name must not contain special characters such as - or ().