First of all, thanks for trying Enpass and writing to us.
Unfortunately the CSV file exported by Dashlane has many issues affecting the clean import of all items. They are like; partial export of data in CSV, Indefinite number of columns and other formatting problems. So, It is nearly impossible to make a good importer.
However the best workaround at the moment is to create your own custom csv by editing the Dashlane’s exported file. Open that in a spreadsheet program and copy columns to a new CSV with format described in this FAQ. https://www.enpass.io/kb/i-want-to-import-database-from-other-password-manager-but-its-not-present-in-enpass-import-list-can-i-still-import-my-database/
After that you will be able to import your passwords using Generic CSV importer.