Pi offline or missing data

1. Check whether the portal API is reachable and whether only collection is stale. Read last-report age rather than assuming an empty chart means zero.
2. Check power and network physically, then try private SSH. Avoid repeated forced power cycles while storage may be writing.
3. On the Pi, inspect uptime, systemctl is-active alloy, systemctl list-timers 'raspberry-*', and systemctl status raspberry-collect@host.service.
4. Check clock synchronization and recent collector errors. Inspect /run/raspberry-telemetry for newly written textfiles. Review private Alloy logs for delivery errors without copying secrets to public tickets.
5. Check DNS/TLS and the ingestion credential. Separate public pipeline failure from private Grafana delivery failure.
6. After repair, verify two consecutive fresh reports, chart updates and a recovery notification. Record gaps honestly; volatile buffers cannot reconstruct samples lost during a reboot.