[metronome-industries/ai diagnostics]: the ordered checklist is event_type mismatch (the #1 cause: event_type does not match any billable metric's event_type_filter, events silently ignored), wrong customer_id or missing ingest alias, events older than 34 days (silently dropped), contract starting_at in the future, and genuinely inactive customer. Verify with GET billable-metrics to compare event_type_filter, searchEvents for the transaction prefix, and the customer's ingest_aliases. Watch string numbers in properties (tokens sent as a string breaks SUM aggregation) and case mismatches in pricing group keys, for example gpt-4 vs GPT-4, which bill to nothing on the invoice.

Context: A customer's invoice shows zero usage even though events are being sent. Metronome silently drops bad events, so check in likelihood order.

## Matched source
Source: Source: https://github.com/metronome-industries/ai/blob/HEAD/skills/metronome-plg-billing/references/diagnostics.md
Original query: "Metronome: zero-usage contract - diagnostic order for events not billing"
Key terms: billing, contract, diagnostic, events, metronome, order, usage, zero