Why my import fail ?
The most probable reason for this is an issue with your csv file.
Your CSV file must meet following criteria:
Has a column count less than 100.
Has a cell count less than 1,000,000.
Has a file size less than 35mb.
Also your file need to have colums with those fields: Email and Is Unsubscribed in order for import to work
Another common reason for import to fail is to use incorrect csv file delimeter when uploading the file. If you are not sure which one is used in your csv file open it in any text editor and check which delimeter is used to separate values,then use correct one when uploading the file