Railsでbcrypt インストール後エラーが出る

Ruby on Rails 6.0.3を利用してアプリ作成を行なっています。

ログイン機能を搭載するためbcryptをインストールしたのですがrails testを実行すると

Traceback (most recent call last):
        22: from /usr/local/bundle/gems/spring-2.1.1/bin/spring:49:in `<main>'
        21: from /usr/local/bundle/gems/spring-2.1.1/lib/spring/client.rb:30:in `run'
        20: from /usr/local/bundle/gems/spring-2.1.1/lib/spring/client/command.rb:7:in `call'
        19: from /usr/local/bundle/gems/spring-2.1.1/lib/spring/client/server.rb:9:in `call'
        18: from /usr/local/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        17: from /usr/local/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        16: from /usr/local/bundle/gems/spring-2.1.1/lib/spring/server.rb:9:in `<top (required)>'
        15: from /usr/local/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        14: from /usr/local/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        13: from /usr/local/bundle/gems/spring-2.1.1/lib/spring/commands.rb:4:in `<top (required)>'
        12: from /usr/local/bundle/gems/spring-2.1.1/lib/spring/commands.rb:33:in `<module:Spring>'
        11: from /usr/local/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
        10: from /usr/local/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
         9: from /usr/local/lib/ruby/2.6.0/bundler/setup.rb:20:in `<top (required)>'
         8: from /usr/local/lib/ruby/2.6.0/bundler.rb:107:in `setup'
         7: from /usr/local/lib/ruby/2.6.0/bundler/runtime.rb:20:in `setup'
         6: from /usr/local/lib/ruby/2.6.0/bundler/runtime.rb:108:in `block in definition_method'
         5: from /usr/local/lib/ruby/2.6.0/bundler/definition.rb:226:in `requested_specs'
         4: from /usr/local/lib/ruby/2.6.0/bundler/definition.rb:237:in `specs_for'
         3: from /usr/local/lib/ruby/2.6.0/bundler/definition.rb:170:in `specs'
         2: from /usr/local/lib/ruby/2.6.0/bundler/spec_set.rb:85:in `materialize'
         1: from /usr/local/lib/ruby/2.6.0/bundler/spec_set.rb:85:in `map!'
/usr/local/lib/ruby/2.6.0/bundler/spec_set.rb:91:in `block in materialize': Could not find bcrypt-3.1.16 in any of the sources (Bundler::GemNotFound)

このようなエラーが発生します。

以下のページの解決方法を試しましたがうまく行きません。
https://qiita.com/totto357/items/1741da83bf642dab99df

ちなみに

Gemfile
1source 'https://rubygems.org'
2git_source(:github) { |repo| "https://github.com/#{repo}.git" }
3
4ruby '2.6.6'
5
6# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
7gem 'rails', '~> 6.0.3', '>= 6.0.3.4'
8# Use mysql as the database for Active Record
9gem 'mysql2', '>= 0.4.4'
10# Use Puma as the app server
11gem 'puma', '~> 4.1'
12# Use SCSS for stylesheets
13gem 'sass-rails', '>= 6'
14# Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker
15gem 'webpacker', '~> 4.0'
16# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
17gem 'turbolinks', '~> 5'
18# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
19gem 'jbuilder', '~> 2.7'
20# Use Redis adapter to run Action Cable in production
21# gem 'redis', '~> 4.0'
22# Use Active Model has_secure_password
23  gem 'bcrypt', '~> 3.1', '>= 3.1.12'
24
25# Use Active Storage variant
26# gem 'image_processing', '~> 1.2'
27
28# Reduces boot times through caching; required in config/boot.rb
29gem 'bootsnap', '>= 1.4.2', require: false