Configuration like this below:

window.__REDUX_DEVTOOLS_EXTENSION__ && window.__REDUX_DEVTOOLS_EXTENSION__()

Please check this link for more detail step by step

github.com/zalmoxisus/redux-devtools-extension

I would look at your repo as soon I'm on a laptop (currently mobile). In the mean time you can take a look at my sample repo where I test my build chain etc. 2 simple pages using redux and some middleware.

github.com/HerrVoennchen/sample-project