Sometimes you will need to make sure that the .CSV file you have is matching our import criteria.
It's important to organize your data based on the headlines. Please note that the first line of the categories needs to be exactly the same as shown in the picture with lowercase letters. Sometimes you will need to add extra categories like note or type if there are none.
To import your passwords, go to Settings → Import/Export → Other if others are not relevant. Then select the .CSV file you want to import and click Open and then confirm by clicking on Import Selected.