Possible causes for an import error may include but are not limited to:
You're using other characters other than letters, numbers, commas, periods, parentheses, and hyphens.
A cell exceeds more than 50 Characters.
Rows that do not contain at least the first name.
Matters without a contact associated to it in the same row of the CSV file.
Other matter items, such as notes, that do not contain a Matter: Name in the import for that row.
You have custom fields set to *Required and the import does not contain some, if not all, required custom fields in the excel sheet.
You're using other types of custom fields other than text field.
Not capitalizing the first letter of the Matter: Status column.
It should be: Open, Pending, or Closed.
Date formats need to be: dd/mm/yyyy