Very basic here.  I'm on the import to data challenge.  I walk through all of the steps and then receive an error after I get the success email.  I'm unsure on how to correct it.  I loaded 20 records and I get a success email with 20 records.  

Challenge not yet complete... here's what's wrong: 
One of the contact records from the CSV file could not be found in the Org.

After importing all Contacts, it is still showing this error. I have tried many times but stuck with the same error. In other org it is working as expected but I am facing this issue in my org. Do not know what is happening here!