All I see are grid lines!

Is the top floor plan level of your linked model not showing up in plan view? Are you just seeing grid lines and no walls or doors? Is there a roof level, and if so, did you create a floor plan for that level? If not, that is the problem. Go to the View Range settings for the level in question. Most likely, the top is set to "Level Above". If you didn't create a plan view of the roof, then technically there is no "level above" and nothing will display in plan view. To fix this, either copy/monitor and create a floor plan view of the roof level, or set the top range of the floor plan level to "Associated Level (Level #)" and enter an offset value of 10'-0", or whatever is required for the visibility of your plan view.