it sounds like your data sources are live rather than extracts. Also - are all the correct drivers installed for tableau server to connect to the data source in question? I typically post my original tableau data source to tableau server as a data source and then change my desktop viz to use the server data source. If this works fine, then I just post the viz to server and set it to refresh daily on a schedule.
If you not the Tableau Server Admin, you might check with him/her to get further assistance as well.