# Error Handling Reference

| Error | Cause | Solution |
|-------|-------|----------|
| `Events not appearing` | DSN, sampling, or filtering issue | Use diagnostic checklist above |
| `Source maps not working` | URL prefix or release mismatch | Verify upload and SDK release match |
| `429 errors` | Rate limit exceeded | Implement sampling and filtering |
| `Missing breadcrumbs` | Integration disabled | Enable Breadcrumbs integration |