Website shows down in monitoring but works for me

Symptoms

Your monitoring reports down, but when you open the site locally it loads fine.

Likely causes (check in order)

1. DNS mismatch: Different resolver answers (split-horizon DNS), stale local cache, or geo-specific DNS routing.
2. Geo or network path: Failure only from certain regions; CDN or edge misconfiguration.
3. Blocking monitoring IPs: WAF, bot protection, or rate limits treating probes as unwanted.
4. TLS/redirect issues: Certificate errors, mixed content, or HTTP→HTTPS loops visible externally.
5. Timeouts: Origin slow only under cross-region latency; cold starts or DB locks.

What to do

• Reproduce from an external vantage (VPN regions, third-party curl).
• Compare response codes and headers from probe vs browser.
• Temporarily allowlist probe IPs or relax WAF for verified probe user-agents (carefully).
• Increase timeouts after confirming genuine slowness vs noise.

Prevention

Multi-location checks, realistic thresholds, and documenting intentional blocks. Keep health endpoints lightweight.