The Method as shown in my examples was "%Next" but you have missed the %.

See this more complete example:

Class Demo.Operations.GetResultsFromLookupTable Extends Ens.BusinessOperation
{

Method OnMessage(pRequest As Ens.Request, Output pResponse As Ens.StringContainer) As %Status
{
    Set tSC = $$$OK
    Set tStatement = ##class(%SQL.Statement).%New()
    Set tQuery = "SELECT * From Ens_Util.LookupTable WHERE TableName = ?"
    Set tTable = "testLookupTable"
    $$$THROWONERROR(tSC,tStatement.%Prepare(tQuery))

    Set tResult = tStatement.%Execute(tTable)
    Set count = 0
    While tResult.%Next(){
	    //Do what you need to with the results here
	    $$$TRACE("Result: "_tResult.KeyName_", "_tResult.DataValue)
        Do $INCREMENT(count)
    }
    Set pResponse = ##Class(Ens.StringContainer).%New()
    Set pResponse.StringValue = count_" results found."
    Quit tSC
}

}

Which gives this in a trace:

Also, please note that in my initial response, I had a mistake in the column names I referenced. I had put "KeyName" and "KeyValue" whereas the second should have been "DataValue" as you already had in your first screenshot.

Additionally, it's best that you avoid concatenation for building the string of your query, and should instead use parameters to avoid issues with unexpected characters breaking your query (or, in some scenarios, opening yourself up to exploits via SQL injection).

My example above should instead be:

Set tStatement = ##class(%SQL.Statement).%New()
Set tQuery = "SELECT * From Ens_Util.LookupTable WHERE TableName = ?"
$$$THROWONERROR(tSC,tStatement.%Prepare(tQuery))

Set tResult = tStatement.%Execute(tTable)

While tResult.%Next(){
	//Do what you need to with the results here
	$$$TRACE("Result: "_tResult.KeyName_", "_tResult.DataValue)

}

Note that the table name is a ? in the initial query string, and the value of the table name is being referenced in the %Execute() method