Change your Model View Options (MVO) from 'Schematic' to 'Full' for Railings.
In the Menu under Document>Set Model View> Model View Options and then under the Stair and Rail Options you should see the options for what to show in the 'Stair and Rail Detail Level in 3D and Section' Settings
Your Rail settings is most likely either set to 'Schematic' or 'Simplified' or it's 'Full' but with everything unchecked except the posts.
Change it to Full to show the full railing.