There are two reasons for why your unit session by product is showing 0.00%.

1.) You have not collected the data for that date using the HelloProfit Chrome extension. If there is no data available for the date, it will display 0.00%. It is important to note that you must download ALL Unit Session Percentage data into HelloProfit for any date range query you make in HP.  For example, if you want to see the Unit Session Percentage for the past 30 days on your Product Dashboard, be certain you've downloaded ALL those days Unit Session Percentage data first from Seller Central. Otherwise, your resulting averages will be skewed.

2.) You are trying to view Unit Session for today. Amazon makes today's Unit Session Percentage data available TOMORROW, so your Unit Session Percentage statistics in HelloProfit (or on Seller Central for that matter) are only available for yesterday and earlier. You will never be able to view today's Unit Session information, as Amazon does not make the current Unit Session data available until the next day.