To ensure that we don't interfere with your live shop, the application is set as "Disabled" as default upon installation. To activate the applications to your customers you manually have to "Enable" it in your Shift4Shop admin. Do so by browsing to the "Drag2Cart Settings" in the menu to the left. Here you will find the setting to enable or to disable the application.
You can enable and disable the application at any time and as many times you like.