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:

“Error
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?