3D problem

[Orsus]

Hi,
I'm a new user
I designed a sketch using your demo file. Then, I made a copy and pasted several pieces of furniture from the demo file to my file and saved the file. After reopening the file, I do not see the 3D; only the sketch and furniture show. I can move the furniture on the drawing, but the 3D cannot be seen.
Please Help [:((]
Avi

[Puybaret]

Is the 3D view grey or does the plan takes all the space vertically?

[Orsus]

The 3D view is grey