Try each of the following steps in order until the issue is resolved:

  1. Remove duplicate records from Import file
  2. Update the Key Indicator in the import file to the letter I (for individual) instead of the number 1
  3. Cut and paste the Key Indicator column so as to make it the last column in the import file
For additional information, see How to import constituent name, address, and phone numbers including multiple phone numbers and email addresses (includes sample data file).