I found my problem in that I have many html files templates, so I forgot to add which html files templates the Following button needs to render to.

views.py:

def post_following(request):
return HttpResponseRedirect(reverse("index"))

urls.py:

    path("post/following", views.post_following, name="post-following"),

layout.html:

<a id="following" class="nav-link" href="{% url 'post-following' %}">Following</a>