Workspace Unavailable

I am not able to visualize my app in workspaces. It shows the workspace is unavailable, following is the next message "This is a preview link for a Treehouse Workspace that is not currently active. If you are the workspace owner, you can launch it again via the Treehouse site."

My code is:

from flask import Flask

app = Flask(name)

@app.route('/') @app.route('/<name>') def index(name="Treehouse"): return "Hello from {}!".format(name)

@app.route('/add/<int:num1>/<int:num2>') def add(num1, num2): return '{} + {} = {}'.format(num1, num2, num1+num2)

app.run(debug=True, port=8000, host='0.0.0.0')

Appreciate any response in advance.