Answer
Workflows use JsonPath to extract values from a REST response, and a JsonPath expression pointing at an array needs to specify which element of the array you want — for a value nested in an array like columns, $.columns.id won't resolve, but $.columns[0].id (specifying the array index) will. Check that your JsonPath expression correctly reflects the actual shape of the response, particularly around arrays, rather than assuming a path that works for a plain object will also work for an array.