Failed to scaffold an app

[taidengyoutiao]

I am trying to scaffold an app according to the dev doc(  https://shopify.dev/docs/apps/build/scaffold-app#step-3-install-your-app-on-your-development-store  )

But in step 3, after I opened my dev store and installed my app, the app page shows "example domain" instead of the content created by the source code.

I don't know how to solve this...