Django2.2.4 - NoReverseMatchが解決しない

Django初心者です。ブログアプリのようなものを作っています。
フォームに入力した内容の詳細を表示させるページに行こうとするとこのようなエラーが出ます。フォームに入力した内容を変更するページ(http://127.0.0.1:8000/KnowHow/1/update/)などは開けるのですが，なぜか詳細を表示するリンク(http://127.0.0.1:8000/KnowHow/1/detail/)にアクセスしようとするとエラーが表示されてしまいます。

NoReverseMatch at /KnowHow/1/detail/
Reverse for 'update' with arguments '('',)' not found. 1 pattern(s) tried: ['KnowHow\/(?P<pk>[0-9]+)\/update\/$']

views.py,detailページのhtml,urls.py,models.pyを置きました。推測でもいいのでコメントを頂けたら幸いです。他にも必要なコードがあればコメントください。

views.py

from django.urls import reverse, reverse_lazy
from django.http import HttpResponse
from django.views import generic
from django.shortcuts import redirect
from django.core.exceptions import PermissionDenied
from django.contrib.auth.mixins import LoginRequiredMixin
from django.contrib.auth.decorators import login_required
from .models import KnowHow


class IndexView(generic.list.ListView):
    model = KnowHow
    paginate_by = 5
    ordering = ['-title']
    # template_name = 'portal/KnowHow_list.html'

#該当の関数
class DetailView(generic.detail.DetailView):
    model = KnowHow
    #template_name = 'portal/KnowHow_detail.html'


class CreateView(LoginRequiredMixin, generic.edit.CreateView):  # The LoginRequired mixin
    model = KnowHow
    fields = ['title','text','basic_tag','free_tags'] 

    #template_name = 'portal/KnowHow_form.html'

    def form_valid(self, form):
        form.instance.author = self.request.user
        return super(CreateView, self).form_valid(form)


class UpdateView(LoginRequiredMixin, generic.edit.UpdateView):  # The LoginRequired mixin
    model = KnowHow
    fields = ['title','text','basic_tag','free_tags']

    #template_name = 'portal/KnowHow_form.html'

    def dispatch(self, request, *args, **kwargs):
        # ownership validation
        obj = self.get_object()
        if obj.author != self.request.user:
            raise PermissionDenied('You do not have permission to edit.')

        return super(UpdateView, self).dispatch(request, *args, **kwargs)


class DeleteView(LoginRequiredMixin, generic.edit.DeleteView):  # The LoginRequired mixin
    model = KnowHow
    success_url = reverse_lazy('portal:index')

    #template_name = 'portal/KnowHow_confirm_delete.html'

    def dispatch(self, request, *args, **kwargs):
        # ownership validation
        obj = self.get_object()
        if obj.author != self.request.user:
            raise PermissionDenied('You do not have permission to delete.')

        return super(DeleteView, self).dispatch(request, *args, **kwargs)


@login_required
def help(request):
    return HttpResponse("Member Only Help Page")

portal/KnowHow_detail.html

html
1
2{% extends 'base.html' %}
3
4{% block title %}Sign up{% endblock %}
5
6{% block content %}
7<h1>{{ object.title }}</h1>
8<section class="KnowHow-text">
9    {{ object.text|linebreaksbr }}
10    <p>Author: {{ object.author }}</p>
11    <p>Free tags: {{ object.free_tags}}</p>
12    <p>Basic tag: {{ object.basic_tag}}</p>
13</section>
14
15
16{# ownership #}
17{% if request.user.id == object.author_id %}
18<section class="KnowHow-edit">
19    <a class="act" href="{% url 'portal:update' KnowHow.pk %}">Edit</a>
20    <a class="act" href="{% url 'portal:delete' KnowHow.pk %}">Delete</a>
21</section>
22{% endif %}
23<section>
24    <p><a href="javascript:history.back()">&lt; Back</a></p>
25</section>
26{% endblock %}

urls.py

from django.urls import path
 
from . import views
# set the application namespace
# https://docs.djangoproject.com/en/2.0/intro/tutorial03/
app_name = 'portal'
 
urlpatterns = [
    # ex: /
    path('', views.IndexView.as_view(), name='index'),
 
    # ex: /KnowHow/create/
    path('KnowHow/create/', views.CreateView.as_view(), name='create'),
 
    # ex: /KnowHow/1/
    path('KnowHow/<int:pk>/detail/', views.DetailView.as_view(), name='detail'),
 
    # ex: /KnowHow/1/update/
    path('KnowHow/<int:pk>/update/', views.UpdateView.as_view(), name='update'),
 
    # ex: /KnowHow/1/delete
    path('KnowHow/<int:pk>/delete/', views.DeleteView.as_view(), name='delete'),
 
    # ex: /KnowHow/help/
    path('KnowHow/help/', views.help, name='help'),
]

models.py

from django.db import models
from django.urls import reverse
from taggit.managers import TaggableManager
    
class KnowHow(models.Model):

    BASIC_TAGS =(
        ('1','a'),
        ('2','b'),
        ('3','c'),
    )
    
    author = models.ForeignKey('auth.User',on_delete=models.CASCADE)
    title = models.CharField(max_length=200)
    text = models.TextField()
    basic_tag = models.CharField(max_length=1,choices=BASIC_TAGS,default='1')
    free_tags = TaggableManager(blank=True)
    
    def __str__(self):
        return self.title
    
    def get_absolute_url(self):
        return reverse('portal:index')