How to preview app changes? And error "shopify.dev refused to connect."

[gracebonnie]

Hi,

I am just following this guide here to start building the app https://shopify.dev/apps/getting-started/add-functionality.

At the end of Step 2: Add an empty state, it mentioned about "When you preview your embedded app, it displays the empty state." I had no idea how to preview the app with the new changes, so what I did was I uninstalled that app in my developer store, and reinstalled it again. However, after that I keep seeing the error "shopify.dev refused to connect." when I tried to load up the app after running "shopify node serve".

I am not sure what's happening here, can anyone help?

Thanks!!