Check your configuration files carefully — the root cause of routing issues can be outside the app folder.

I encountered a tricky problem where Next.js route interceptors stopped working because of misconfigured i18n setup in the config files. The React components and app folder were fine, but the issue was in how next-i18next config was integrated into next.config.js.

For a detailed explanation and solution, see my article: https://dev.to/antononoprienko/how-i18n-in-nextjs-broke-my-route-interceptors-and-how-i-fixed-it-18mb