I have a Next.js 14.2 webapp with App router and try to include an open-graph image by exporting static metadata in the rootlayout file:

export const metadata = {
  metadataBase: new URL(`${process.env.NEXT_PUBLIC_BASE_URL}`),
  title: {
    default: "my-title,
    template: '%s | my-title'
  },
  description: "Some description",
  twitter: {
    card: "summary_large_image"
  }
};

The opengraph-image is located in the app/ route under the exact name: opengraph-image.png.

It works in development mode on localhost:3000 but when I deploy the app to heroku the image is not showing up.
The og-image tag is included in the header:

but when I try to navigate to it heroku says:

There's nothing here, yet.
Build something amazing

Any ideas how to fix it?