Populate select from query

I am creating a simple app where I populate a select list from an SQL query. I can see the data coming through on the preview of the query called sqlCountries. I have tried setting the data source as {{ sqlCountries.data }} and {{ formatDataAsArray(sqlCountries.data) }}, but nothing is displayed in the select component.

SQL:

Select:

I am unsure why the data source says "The selected data source is empty." In dynamic view, I have used:

But have also tried:

Tested this and didn't run into any problems

Checking the obvious (and issue I've run into many times when troubleshooting) - Have you saved the query?
Your screenshot shows it's in preview only

Good point, but it is saved.

Solution found: the query needed the advanced option "Run this query on page load" turned on.