It should work if the query string is url encoded and it is in the correct part of the url for where it will be looked for on the server side. This is most likely after the appInstance but before the stream name.
Please try the following:
1. Form the query string so that everything is url encoded (including ?, = and &).
2. Include the appInstance name.
3. Do not include a forward slash "/" between the appInstance name and the query string.
4. Do include a forward slash "/" between the query string and the stream name.
5. Leave the stream name in the last part of the url. If the query string is left on the end after the stream name then it will be treated as a stream level query string.