The message that you are getting - "Insufficient balance", means that you have the below function turned on (you've probably clicked "Yes, please" before profile visiting or selected email collection option in Dux-Dash)
Regular and Expert UI
If you clicked "Yes", this means that Dux-Soup is looking and scraping emails of your 2nd and 3rd-degree connections. Dux-Soup is able to obtain the email addresses of your 1st-degree connections for free. However, if you wish to obtain emails of your 2nd and 3rd-degree connections you would need to purchase Dux-Soup Points.
How to turn it on or off
If you do not wish to use this function and you did not intend to scrape emails of your 2nd and 3rd-degree connections, turn this function off by clicking "No, thank you" on the popup window.
Or go to https://app.dux-soup.com/web/dux-store and untick the following: