COLLADA export problem

[FEAR]

i didn't skipped any step, but i didn't read the rest of the page
EDIT: if i open an entity of a custom story with the model editor it show the model but if i open with blender ( import/collada file ) it doesn't show anithing. Is a blender export problem?
2° EDIT: i tried again importing entity in blender and it work
3° EDIT: i exported the model ( not my box ) with blender and the model editor now show the model