For Google Sheets, please be sure to export it as a .csv format file.
Your list uses a legacy Excel format
Microsoft Excel can export CSV files in a variety of different formats, make sure to select " CSV UTF-8 (Comma delimited) (.csv)" when saving your list.
Selection of correct file format
Your list does not contain column headers in the first row
Make sure that your CSV file contains your column headers in the first row. Any other text or information in that first row will create an error when uploading your list.
APNs are formatted as exponential numbers
Commonly, APN numbers can be formatted as an exponential number, rather than a text field, causing rows to have duplicate APNs.
Pebble treats a property as unique based on its county and APN. When it sees a duplicate APN, it'll assume you want to update the record that already exists.
If you're using Excel, make sure the column is set to "text", and not "general" or "number". Then when you save as a CSV, it should come out correct.