app.css.config.serve_locally = True
app.scripts.config.serve_locally = True
If you are using external CSS or JS, then add them to the top of your layout with e.g.
css_link = '/static/my-stylesheet.css' # update with your stylesheet. could be https://... as well
js_link = '/static/my-script.js' # update with your custom JS link if applicable. again, could be a remote url prefixed with e.g. https://... as well
app.layout = html.Div([
# ... the rest of your app