Django nested categories - path getting 404 on child slug - django

Question

I try to create nested categories with django-treebeard.
And in admin this solution work fine. But I need to show this categories. When I try reach root category eq.: /kategorie/wegetarianskie then works fine, but when I try to reach fullslug with children category eq.: /kategorie/wegetarianskie/obiady then I have error 404 and don't know why.
Maybe someone have answer.
My model:
class Category(MP_Node):
name = models.CharField(max_length=255, verbose_name='Nazwa kategorii')
slug = AutoSlugField(populate_from='name', unique=True)
fullslug = models.CharField(max_length=255, verbose_name='Pełny adres kategorii', blank=True)
created_at = models.DateTimeField(default=datetime.datetime.now)
node_order_by = ['name']
Then with signal I create full slug like this:
#receiver(post_save, sender=Category)
def save_parentname(sender, instance, **kwargs):
if not instance.fullslug:
if instance.is_root():
instance.fullslug = instance.slug
instance.save()
else:
catslug = '/'.join([instance.get_parent().slug, instance.slug])
instance.fullslug = catslug
instance.save()
When child category is save, then signal create full slug like: /kategorie/wegetarianskie/obiady
I have also get_absolute_url:
def get_absolute_url(self):
return reverse('categorydetail',
args=[self.fullslug])
View:
def category_detail(request, fullslug):
category = Category.objects.get(fullslug=fullslug)
return render(request, 'categories/category_detail.html', { 'category': category })
Urls:
urlpatterns = [
path('wszystkie', views.category_list, name='categorylist'),
path('<fullslug>/', views.category_detail, name='categorydetail'),
]