If the import system cannot read your file, it is due to the columns.
Your document should follow the import's guideline. All columns presented in the import page should be in your document.
You also need to know that for Squowk to process all this information it is important to use the column's format indicated in the import page. Any other format will not be recognized by the system and some flight won't be processed.
You can find a template for the import file format here