You will need to provide a little more information as to which data sources you are refreshing from. Also, what error message do you get when you view your background tasks in the maintenance section.
You won't get any feedback on the screen where you see "1 task submitted for refresh", but have you checked the background tasks dashboard to see more detail?
Tableau Server has background processes that handle refreshes (and other maintenance and cleanup). You can see what's going on by clicking on "Maintenance" under Administration and then "Background Tasks".
From there you can see the progress of the extract and whether it succeeds or fails and error messages, if any.