[Answered ]-Unexpected Keyword argument using formset_factory

You pass this as form_kwargs=… parameter ^[Django-doc], so:

class AddNotaBlock(FormView):
    template_name = 'notas/insertar_nota.html'
    form_class = formset
    success_url = reverse_lazy('home')

    def get_form_kwargs(self):
        kwargs = super().get_form_kwargs()
        kwargs.setdefault('form_kwargs', {})['request'] = self.request
        return kwargs