This happens when information on the spreadsheet is not formatted correctly.
Make sure that the Heading for the column on the spreadsheet is written exactly as it should be. Any slight misspelling, extra spaces, or extra characters will cause the entire column to be ignored.
Values Formatted Incorrectly
If the value is supposed to be a numeric value, make sure it is not formatted as a formula.
Using Incorrect Template
If you are working with a template, especially if it's one you've created yourself, you will need to make sure that it is 100% up to date. You can either download the most current Brandboom template from the Import Products panel or use an exported file.