In the import file, try the following to resolve the error: 
  1.  Highlight and delete the empty rows below the import data
  2.  Highlight and delete the empty rows to the right of the import data
  3.  Check if there has been any data that was copied and pasted into the excel file( such as email text). If so, then the text may contain special line break characters placed there by the program or software that the text was originally in. To check for the special characters: 
    1. ​Get a copy of the import file
    2. Copy and paste the suspected text into notepad ++ 
    3. In notepad++, click the option to show all characters. 
    4. Look for blocked characters, (letters in a black box), usually at the end of a line or where an apostrophe should go. Delete these characters and then cut and paste this into the excel file
    5. Repeat for any other suspected text in excel file
    6. Save and close the import file when completed.
  4. Once the import file has been saved with the changes, re-import the file.