Plotly Dash Dropdown Callbacks

I have created a network of items purchased together in a main graph with is searchable through a function that returns a subgraph. I have dropdowns on my dashboard to input the item and store I want the subgraph to be made from but am having trouble with getting my callbacks to work. If someone could give me pointers or code on how to get everything to talk that would be great! Currently, when I select something from my dropdowns in my webpage nothing happens. Thanks!