What is a "wide series" and how would this alarm error be resolved?

I am trying to set an alarm where if I don’t hear from a IOT thing within a certain time I want the alarm set. I have a query that works at AWS Timestream but I can’t get the query result in the right format. I get a super cryptic error message:

Failed to evaluate queries and expressions” failed to execute conditions: input data must be a wide series but got type not (input refid)"
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What is a “wide series”? How do I make sense of this error message?

I did some research…
There are two kinds of series: “long” (and narrow) and “wide” (and short).
The name refers to the shape of the table that holds the time-series data.

If all of the sample data has it’s own column then it’s called “wide”. The header tells you what the data is.

If there is only one column for the sample data and an extra column that tells you what data it is than that is called “long”.

Grafana alert queries expect the data to be “wide”, not “long”.