When I extrude a 2d SubDPlane it shrinks back

Hi im learning Rhino.
So i’m trying to extrude via gumball dot to create a roof shell but it shrinks back. I’m trying to do 3:06 at this video: Zaha Hadid Architects - Rhino Tutorial - YouTube

Please tell me what i do wrong.

wow. what a great community…

you need to help us help you a bit…we need more detail about your problem.

can you post your file?

is this subd plane or a curve?

if it’s a curve Is your curve rebuild to be subd friendly?

can you post a video of your process? following the zaha video works fine here.