Slab is Unseen, when I set the 'Reference Plan Location' on top.

[kimaa]

Hello.

Suddenly, When I make 'Slab' with 0 elevation is Unseen on Home story. (It appeers on below story).

How can I solve it?

I have uploaded my test file, thanks.

[Laszlo Nagy]

I think you have the "Show on Stories" field set to "All Relevant Stories" before you try to place the new Slab.

The left Slab in your file is set to "Home Story only", while the right one is set to "All Relevant Stories".

When it is set to "All Relevant Stories", it decides to display the Slab or not based on whether the body of the Slab falls within the vertical display range on the current Story as set in the Floor Plan Cut Plane Dialog. 

The trick you can do is to set the Show down to" field to a negative value, so it will extend a bit into the Story below the current story and then the Slab will fall into the vertical display range. Please note that the Floor Plan Cut Plane is saved with Views so you may have to modify the settings of saved Floor Plan Views as well.