I am having the same issue with trying to upload a list of emails from a CSV file to populate a list.
My CSV file consists of one column headed with "email" and then a list of emails below it. I've also tried a CSV file that has headers of First Name, and Last Name as well. I've tried using all three choices of field separators with the same results. It tells me the import is complete, however nothing is being imported:
Import completed: 0 errors, 0 added, 0 updated, 0 skipped.
When I copy the data from the CSV file and paste it into the CSV Text window, the import works. However, not ideal for a list with hundreds of emails.
I am using Chrome (version 66.0.3359.181) on a Mac computer (10.13.4).