z-levels and layers

I have two problems with my ceiling drawings that i'm working on. I think the information on the drawing originally comes from a Revit model.

The drawing, which is supposed to be a 2d drawing has information on several Z-levels. I'm trying to flatten the drawing using the FLATTEN command, but it doesn't work.

The second problem is that layers that are non visible are turned on and are not freezed. I've also checked the model file and they are turned on there as well, although here they are visible.

If anyone has a clue I'd be thankful. Could these two problems be related?

Maybe those layers are set to be frozen in the viewport itself.

There are a few different methods to flatten geometry so that Z=0. See attached document.

How to flatten entities in AutoCAD to Z=0.doc

Ok. Thanks. And how do I control the layers in the viewport?

Via the Layer Properties Manager. There is an option to freeze a viewport layer (VP Freeze).

As shown in the image of the LAYER PROPERTIES MANAGER;

or you can double click into the viewport in question, then check in your LAYERS dropdown toolbar to see if there are any layers which are viewport frozen in that specific viewport.

Ok. Thanks. And how do I control the layers in the viewport?

Activate Model Space through the ViewPort you wish to make changes to, open the Layer Properties Manager and scroll to the Right.