form_withでRouting error

ruby on rails6

form_with使ってデータを作成したいのですが、以下のようなエラーが発生します。

Routing Error
No route matches [POST] "/admin_users/new"

上記のエラー通りにnewにポストを付与してあげた。

post 'admin_users/new' => 'admin_users#new'

を追加したのですが、createされてないようなので何が原因なのでしょうか。

view
1<%= form_with(model: @admin_user, local: true) do |form| %>
2        <%= render 'shared/error_messages', model: form.object %>
3          <fieldset class="inputs">
4            <ol>
5              <li class="string input optional stringish" id="item_name_input">
6              <%= form.label :email %>
7              <%= form.email_field :email,class: 'form_field', autofocus: true, autocomplete: "email" %>
8              </li>
9              <li class="string input optional stringish" id="item_price_input">
10                <%= form.label :password %>
11              <%= form.password_field :password,class: 'form_field', autocomplete: "current-password" %>
12              </li>
13              <li class="number input optional numeric stringish" id="item_stock_input">
14                <%= form.label :membername %>
15              <%= form.text_field :membername %>
16              </li>
17            </ol>
18          </fieldset>
19          <fieldset class="actions">
20            <ol>
21              <li class="action input_action " id="item_submit_action">
22                <%= form.submit "メンバーを追加" %>
23              </li>
24              <li class="cancel">
25                <%= link_to '取り消す', admin_users_path %>
26              </li>
27            </ol>
28          </fieldset>
29        <% end %>

controller
1  # GET /admin_users/new
2  def new
3    @admin_user = AdminUser.new
4  end
5
6  # GET /admin_users/1/edit
7  def edit
8  end
9
10  # POST /admin_users
11  # POST /admin_users.json
12  def create
13    @admin_user = AdminUser.new(admin_user_params)
14
15    respond_to do |format|
16      if @admin_user.save
17        format.html { redirect_to admin_users_path, notice: 'Admin user was successfully created.' }
18        format.json { render :show, status: :created, location: @admin_user }
19      else
20        format.html { render new_admin_user_path }
21        format.json { render json: @admin_user.errors, status: :unprocessable_entity }
22      end
23    end
24  end
25
26  # PATCH/PUT /admin_users/1
27  # PATCH/PUT /admin_users/1.json
28  def update
29    respond_to do |format|
30      if @admin_user.update(admin_user_params)
31        format.html { redirect_to @admin_user, notice: 'Admin user was successfully updated.' }
32        format.json { render :show, status: :ok, location: @admin_user }
33      else
34        format.html { render :edit }
35        format.json { render json: @admin_user.errors, status: :unprocessable_entity }
36      end
37    end
38  end
39
40  private
41    # Use callbacks to share common setup or constraints between actions.
42
43    # Only allow a list of trusted parameters through.
44    def admin_user_params
45      params.require(:admin_user).permit(:membername, :password, :email)
46    end
47

route
1Rails.application.routes.draw do
2  resources :customers, only: [:new, :create, :show, :index, :update, :edit, :destroy] do
3  	resources :exchange_histories
4  	resources :point_histories
5  end
6
7  root to: 'admin_users#index'
8
9  devise_for :admin_users
10  resources :admin_users
11  post 'admin_users/new' => 'admin_users#new'
12end
13