If the above answers don't work for you (didn't for me), Gatsby keeps a copy of a config.json here ~/.config/gatsby/config.json.

Deleting the file made it work for me.

Relevant Github issue from the Gatsby repo

// clean gatsby cache
gatsby clean
// delete node modules, cache and public folder.
rm -rf node_module .cache public
// reinstall node modules
npm install
// run gatsby in develop mode
gatsby develop
// build the gatsby project
npm run build
// serve the building project.
gatsby serve

workaround 1

add 404.js or 404.tsx file inside pages folder if you don't

1. Try to uninstall the build .cache, and node_modules.
2. yarn add pkg.json npm install *
3. pass all the required props to the layout (comp) in all the pages that it was used.
4. run the gatsby develop before gatsby build

workaround 2

probably you're using React.lazy suspense in your component which doesn't support server-side render, you need to remove it by any possible way. then try this should work!

Want to use React.lazy in Gatsby