Problems with NLA editor and procedure

Hi there,
Sorry if I make a silly question… please help me!!!
Could you please help me?
The problem are the follow:
I have 10 object in the scene. I want to move the object. I use NLA editor. I duplicate my object in the first frame and I insert using key loc. When I move in other frame… the object duplicate disappear not only in the frame but also when I come back in the first frame.
What I did wrong?
Thanks for the patience and for any collaboration!