ActionTextのcontentについて

Question

結論　『リッチテキストが表示されない』

キータを参考に実装をしましたが、リッチテキストが表示されません。
contentの箇所が入力できない状態になっております。
https://gyazo.com/ae0de50e9eae21ecd14edd0a38897ccf

ご教授お願いいたします。

該当のソースコード

posts > _form.htnml.erb

<%= form_with(model: post, local: true) do |form| %>
  <% if post.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(post.errors.count, "error") %> prohibited this post from being saved:</h2>

      <ul>
        <% post.errors.full_messages.each do |message| %>
          <li><%= message %></li>
        <% end %>
      </ul>
    </div>
  <% end %>

  <div class="field">
    <%= form.label :title %>
    <%= form.text_field :title %>
  </div>

  <div class="field">
    <%= form.label :content %>
    <%= form.rich_text_area :content %>
  </div>

  <div class="actions">
    <%= form.submit %>
  </div>
<% end %>

posts_controller

class PostsController < ApplicationController
  before_action :set_post, only: [:show, :edit, :update, :destroy]
  before_action :move_to_index, except: [:index, :show]

  # GET /posts
  # GET /posts.json
  def index
    @posts = Post.all
  end

  # GET /posts/1
  # GET /posts/1.json
  def show
  end

  # GET /posts/new
  def new
    @post = Post.new
  end

  # GET /posts/1/edit
  def edit
  end

  # POST /posts
  # POST /posts.json
  def create
    @post = Post.new(post_params)

    respond_to do |format|
      if @post.save
        format.html { redirect_to @post, notice: 'Post was successfully created.' }
        format.json { render :show, status: :created, location: @post }
      else
        format.html { render :new }
        format.json { render json: @post.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /posts/1
  # PATCH/PUT /posts/1.json
  def update
    respond_to do |format|
      if @post.update(post_params)
        format.html { redirect_to @post, notice: 'Post was successfully updated.' }
        format.json { render :show, status: :ok, location: @post }
      else
        format.html { render :edit }
        format.json { render json: @post.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /posts/1
  # DELETE /posts/1.json
  def destroy
    @post.destroy
    respond_to do |format|
      format.html { redirect_to posts_url, notice: 'Post was successfully destroyed.' }
      format.json { head :no_content }
    end
  end

  private
    # Use callbacks to share common setup or constraints between actions.
    def set_post
      @post = Post.find(params[:id])
    end

    # Only allow a list of trusted parameters through.
    def post_params
      params.require(:post).permit(:title, :content)
    end

    def move_to_index
      unless user_signed_in?
        redirect_to action: :index
      end
    end
end

posts_model

class Post < ApplicationRecord
  has_rich_text :content
end

試したこと

参考サイト：
https://qiita.com/tomokiyao/items/3c22ca9cb916d5c99ca4
https://qiita.com/774ihara/items/3523c109f4e874c31cc4