Django CMS无法向嵌套插件添加子插件

出于某种原因，我似乎无法添加子插件：

我希望实现以下层次结构：

• 常见问题行
  • 常见问题专栏
    • 常见问题

但是，当我按下该列的加号时，什么也不会发生，我无法拖动常见问题列中的常见问题插件。有什么想法吗

我的插件定义：

from cms.plugin_base import CMSPluginBase
from cms.plugin_pool import plugin_pool
from django.utils.translation import ugettext_lazy as _
from .models import FaqPluginModel


class FaqRowPlugin(CMSPluginBase):
    name = u'Faq Row'
    module = _("Fundbox")
    render_template = "faq_row.html"
    cache = False
    allow_children = True


class FaqColumnPlugin(CMSPluginBase):
    name = u'Faq Column'
    module = _("Fundbox")
    render_template = "faq_column.html"
    cache = False
    allow_children = True
    require_parent = True


class FaqPlugin(CMSPluginBase):
    name = u'Faq'
    module = _("Fundbox")
    model = FaqPluginModel
    render_template = "faq.html"
    cache = False


plugin_pool.register_plugin(FaqRowPlugin)  # register the plugin
plugin_pool.register_plugin(FaqColumnPlugin)  # register the plugin
plugin_pool.register_plugin(FaqPlugin)  # register the plugin