Fly.io Common Errors Overview Quick reference for the most common Fly.io deployment and runtime errors with solutions. Error Reference Health Check Failed Causes: App not listening on correct port, slow startup, missing dependencies. Fix: Deployment Failed — Image Build Fix: Machine Won't Start Fix: Connection Refused on .internal Fix: Volume Mount Failures Fix: Rate Limited by Machines API Fix: Implement backoff. See . Quick Diagnostic Commands Resources - Fly.io Status - Fly.io Community - Fly Docs Next Steps For comprehensive debugging, see . ---