You might get a 0 HTTP status code for the following reasons:

• Network issues
  • Internet connection failed during the request so no response was received.
  • A cross-origin request was blocked by the browser because of CORS issues.
  • DNS or firewall issues: There was a problem resolving the server’s address via a DNS lookup or a firewall blocked the request.
• Aborted request
  • If you manually abort a request or the request was aborted indirectly, you might get a 0 status code, indicating the request was cancelled before completion.

Sources & further reading

• StackOverflow answer