React Router with React 16.6 Suspense "Invalid prop `component` of type `object` supplied to `Route`, expected `function`."

Try using render prop instead of component

<Route path="/" render={()=> <Prime />} exact />
<Route path="/demo" render={()=> <Demo />} />

This will be fixed in react-router-dom version 4.4+ as this issue suggests

You can wait for the final release or if you don't want to change your code today, you can install the beta version now by yarn add react-router-dom@next