Wrong date format
On your CSV files, the date can come in a different format. You can tell the converter how dates (M/D/Y vs D/M/Y vs Y/M/D) are supplied on your CSV file (check the source tab to confirm).
The Transactions tab always show dates in Y/M/D format to avoid confusion (this is how converter understands your dates). Change expected date format if date format was not picked up correctly.