Why import may 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 columns with these fields: Email and Is Unsubscribed in order for import to work.

Another common reason why import fails is using incorrect csv file delimiter 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 delimiter is used to separate values, then use correct one when uploading the file.