Running on Prestashop 1.5.3.1 with Appixia module 1.0.2
Showing the categories list does not need to start from root, as it shows the "Home" category only.
How do I fix it?
By default, the Appixia module for Prestashop starts the category tree from the first category (id 1).
Prestashop 1.3-1.4 used to place all of your store categories under the root.
Prestashop 1.5 places all of your store categories under category Home under the root.
This is why you're seeing the Home category first.
This is easy to customize. In Appixia Dashboard, focus on the CategoryList module (if you can't find it, go to "All Modules" list or use the module graph). Go to the inactive settings of this module and look for a property called Filter. This property will allow you to define an initial filter for the category list.
The filter you need is based on category ParentId, meaning filter the list to start from categories with a specific parent - in your case Home category. Assuming the Prestashop category id for Home in your store is 2, you will need to put 2 in the filter value.