Can't see web preview

I want to deploy my github project with streamlit app through vertex ai. it’s very good and useful to deploy a streamlit app on google cloud via Project IDX, I liked it very much.
But in the end I couldn’t see a Web Preview on the app as defined by Gemini. Unfortunately, I couldn’t see the web page given by port name, if it was ok I would deploy the app very easliy.

Do you have a link to the documentation you are following? Could you tell me more about what you mean by - you couldn’t see the web preview of the app? Is the preview not loading? Are you using a blank IDX template to create a workspace?

Just FYI previews work on port 9002 so maybe try running it on that port and see if it works