Issue Description
You have set up a Cover Fill for your Stair Symbol on floorplans, but when you open your View, you notice the Fill is transparent even for the stair's visible segment on this level.
Solution
A Stair's Cover Fill can be enabled or disabled by the Model View Options. This setting will have a higher priority than the Stair's settings, and Graphic Overrides.
1. Go to Document > Model View > Model View Options...
2. Expand the Detail Level of Stair and Railing Symbols tab.
3. Find the Grid Fill and Structure Fill on the SYMBOL COMPONENT list.
4. Change the SHOW setting from None to Visible & Hidden Parts or Visible Parts Only.
5. Click OK.