Prismic Preview not working properly. How to get Prismic Preview work properly?

Question

I've followed the official documentations:

1. https://prismic.io/docs/previews-gatsby
2. https://prismic.io/docs/technical-reference/gatsby-plugin-prismic-previews
3. https://community.prismic.io/t/troubleshooting-previews/5449
4. I've even tried all the solutions mentioned in prev Github issue v4: https://github.com/prismicio/prismic-gatsby/issues/384.

But no luck, always gives error A configuration object could not be found. Check that the repository is configured in your app's withPrismicPreview and withPrismicUnpublishedPreview.

Code snippet from: https://prismic.io/docs/previews-gatsby.

I've asked the same on Github: https://github.com/prismicio/prismic-gatsby/issues/534.