input controls/parameters dialog empty when calling report via URL

Hi,
Typically I embed reports in an iframe via a call to jasperserver using a URL like so;

url = "http://myserver:8080/jasperserver/flow.html?_flowId=viewReportFlow&standAlone=true&_flowId=viewReportFlow&ParentFolderUri=%2Freports%2Fsamplereports&reportUnit=%2Freports%2Fsamplereports%2Freport1&j_username=reporting&j_password=reporting&theme=embed";
 

or via REST like so;

url = "http://nwp-wmlocal1.nwp.usace.army.mil:8080/jasperserver/rest_v2/reports/reports/Basin_Reports/auto_basin_run_report.html" and passing params in the PUT request, etc.
 

Both of these methods work fine.

However, when I call/embed a report that has user input controls/parameters, the dialog (or the on screen section to display them) always comes up blank ?

The params work just fine when running the report from within the jasper reports repository using the web interface, selecting them from the repository, or from iReport etc.

Am I perhaps missing a parameter I need to pass or something to get the embedded report viewer to display the input controls ?

Thanks for any help or suggestions !