TreeTable collapse expand icons not showing

Hi All,

I implemented the a tree table with data binding, which is working correctly. The problem is that I cannot see the expand and collapse icons. When I inspect the css and html, the nodes are suppose to have the title "Expand Node" or "Collapse Node", but all are just named "Node" and only loads the style for a normal leaf node.

Here is a screenshot of the data:

Any assistance with this would be much appreciated!