Hi Railway Support Team,

I'm experiencing a critical issue with my production service hosted on Railway. All requests from my frontend are suddenly being blocked by CORS, even though everything was working perfectly before and I haven’t changed anything in my backend or CORS configuration.

From one moment to the next, every endpoint started returning:

• “Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource.”

• net::ERR_FAILED

• Failed preflight OPTIONS requests

These errors affect all routes, including:
/users/check-user-exists, /practice-preferences, /failed-questions, /subjects, /all-exams, /unanswered-questions, etc.

My frontend origin is:
https://www.simulia.es

My backend is deployed on Railway at:
https://simulia-new-production-f21e.up.railway.app

I verified that:

• The CORS middleware is still correctly configured.

• The server code hasn’t changed.

• The domain hasn't changed.

• The issue occurs only in Railway — when running locally, everything works normally.

This is breaking production for paying users, so I need urgent assistance.

Could you please help me diagnose what changed or what may be causing Railway to stop sending CORS headers on preflight requests?

Thank you very much for your support — this is quite urgent as the platform is currently unusable for my users.

Best regards,
Cristina