colabcode JupyterLab doesn't display JupyterDash.run_server()

[rkzw]

I opened colabcode JupyterLab with

import colabcode as cc
cc.ColabCode(port = 10000,  lab = True , authtoken=authtoken, mount_drive=True)

and run the code below.

from jupyter_dash import JupyterDash
import dash_html_components as html
app = JupyterDash(__name__)
app.layout = html.Div('Minimal')
app.run_server(mode='external')

It does show the sentence Dash app running on: followed by nothing without any error.

I run the same code on the JupyterLab with a local venv and it works.
Is there any way to solve this?