hello
sorry the late reply to this.
the problem was that when i made the export, the cell table of the main category id should be null and there was not. somehow was filled with a zero. that leads to neither that appears on index front end, nor the sub-categories of that, because there are not any category with id zero.
at that time i don't notice that. only after a second look.
thanks to those that try to help on this.