why is the redux state not updated?

Within your state you have a property called userInput, which is the state section controlled by userInputReducer. That section has its own property which is also called userInput that stores the actual data. It that what you intended?

If so, you need to map properties like this:

const mapStateToProps = (state) => ({
    thickness: state.userInput.userInput.thickness
})

If not, you need to rework your userInputReducer and initialState to remove the double nesting.

Everything Seems Fine to me, the Console logs work in the Action and in the Reducer but the Chrome Redux tools show no action being trigged and no state updates.

This sounds to me like an issue with dispatching an asynchronous thunk action. Redux cannot handle these types of actions without the appropriate middleware. When you create the store, it should be something like this:

import reducer from "./reducer";
import {createStore, applyMiddleware} from "redux";
import thunk from "redux-thunk";

const store = createStore(reducer, applyMiddleware(thunk));

I copy and posted your reducer code with a store set up as above. I used a dummy component ( a button that increments thickness when clicked ) and I was not able to reproduce your issue. That leads me to believe that the issue is in the configuration of the store itself.