External Question Schema link does not work

I am trying to include my game URL that is hosted on AWS EC2 instance while creating the HIT

<?xml version="1.0" encoding="UTF-8"?><ExternalQuestion xmlns=" http://mechanicalturk.amazonaws.com/AWSMechanicalTurkDataSchemas/2006-07-14/ExternalQuestion.xsd"> <ExternalURL>myURL</ExternalURL> <FrameHeight>0</FrameHeight></ExternalQuestion>

But, I get the following error here was an error parsing the XML question or answer data in your request. Please make sure the data is well-formed and validates against the appropriate schema. Details: cvc-elt.1.a: Cannot find the declaration of element 'ExternalQuestion'. (1710126470688 s)