Portal Request Create Property Panel UI kit app: Validation error: Invalid data format

Dear all,

I tried to copy the code from the guide: https://developer.atlassian.com/platform/forge/ui-kit-components/jira-service-management/portal-request-create-property-panel/

But when I run the app, I can only see the error message:

"message": "Validation error: Invalid data format.",
"name": "FUNCTION_ERR",
"stack": "Error: Validation error: Invalid data format.\n at ErrMessages (index.js:204:15)\n at Object.onChange (index.js:215:13)\n at index.js:58:30",

The code is:

import ForgeUI, { PortalRequestCreatePropertyPanel, render, Text } from "@forge/ui";

const App = () => {
  return (
      <Text>Hello, world! This is a Forge Portal request create property panel.</Text>
export const run = render(<App />);

Is there anything that I have implemented wrongly? Thank you very much.