Can you explain what you mean exactly by "I can't display my maps in arcgis online."?
If you have map documents, layer packages, etc. these can't be displayed interactively in arcgis.com. ArcGIS.com can only display map services hosted on an ArcGIS Server.
If you have services and these are not displaying properly, can you provide the URL to your server so we can have a look?
Thanks,
Mike