Reporting Services :: Added Parameter In Report Builder Now Missing Query Results

So, this is my Query for dataset "SalesOrder":

SELECT
SO_Header.Customer
,SO_Header.Status
,SO_Header.Customer_PO
,Customer.Name
,SO_Header.Order_Taken_By

[Code] ...

I would like to have a parameter on my report to Select by Order_Taken_By. My attempt at that is here:

Dataset called OrderTaken:

select distinct SO_Header.Order_Taken_By
from SO_Header
Under the report Parameter Properties named @Order, under Available Values
Selected "Get Values from a query"

I have DataSet: OrderTaken

Value Field: Order_Taken_By
Label Field: Order_Taken_By

The values of the field Order_Taken_By is all text characters, no integer values.

Running the inital Query by itself yields results. When I add the parameter, I can make a selection, but now I get no results, even though there should be values for the choice I've chosen.