The window timeout value is the number of seconds Silk Test Classic waits for a window to display. If the window does not display within that period, the Window not found exception is raised. For example, loading an Apache Flex application and initializing the Apache Flex automation framework may take some time, depending on the machine on which you are testing and the complexity of your Apache Flex application. In this case, setting the Window timeout value to a higher value enables your application to fully load.
If the window is on the screen within the amount of time specified in the window timeout, the tag for the object might be the problem.