Monitor stuck on No Data: query matches nothing or window is wrong

TL;DR

Cloning a monitor for a new service and forgetting to update the tag filter. The clone watches the old service (fine) or nothing (no data), and nobody notices until the incident the monitor was supposed to catch.

Steps

1. - Validate the query in the explorer first, monitor second.

• Set notify_no_data deliberately, not by accident.
• For sparse metrics (batch jobs, cron), use wider windows and consider anomaly or new-value detection instead of thresholds.

When to use

You are seeing this: What you see: the monitor never goes OK or Alert, just No Data, forever. Use this skill when you run into "Monitor stuck on No Data: query matches nothing or window is wrong".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The query matches nothing.

Datadog monitor evaluation is query-driven: no matching series means no data state, and monitors expose no-data notification settings; the Terraform monitor example in the docs sets notifynodata explicitly. Verified against live docs 2026-09-26.