@AshNaz87 Ah, the default content was throwing me for a loop, but of course the reason it is there is because your personal content isn’t making it through the build process.
I’m afraid I don’t use Gatsby, so I can’t be as much help as others might. Have you checked this post?
Finally, this might not be a problem with Netlify. It seems you were able to build the default Gatsby instance successfully. The fact that it will not update indicates that you made some edit that upset the build process. If I were in your position, I would download another instance of that same Gatsby template into a separate project, then do a folder comparison to see what has changed in the key files that define the build settings.