bundle install --without production 実行時のエラーCould not fetch specs from https://rubygems.org/について

前提・実現したいこと

cloud9でrails tutorialに沿ってrails new を実行し、gemfileを編集しbundle install --without productionを実行したところエラーになってしまったので解決方法を知りたいです。今までbundle installはできていました。

発生している問題・エラーメッセージ

Fetching source index from https://rubygems.org/

Retrying fetcher due to error (2/4): Bundler::HTTPError Could not fetch specs from https://rubygems.org/
Retrying fetcher due to error (3/4): Bundler::HTTPError Could not fetch specs from https://rubygems.org/
Retrying fetcher due to error (4/4): Bundler::HTTPError Could not fetch specs from https://rubygems.org/
Could not fetch specs from https://rubygems.org/

bundle update を実行しても同じエラーが起こります。
また、ググるとgem update --systemを行うと直ると書いてあったので試したところ次のエラーが表示されました。

ERROR:  While executing gem ... (Gem::RemoteFetcher::UnknownHostError)
    no such name (https://rubygems.org/specs.4.8.gz)

該当のソースコード

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails',      '6.0.3.2'
# Use Puma as the app server
gem 'puma',       '4.3.5'
# Use SCSS for stylesheets
gem 'sass-rails', '6.0.0'
# Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker
gem 'webpacker',  '4.2.2'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '5.2.1'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder',   '2.10.0'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 4.0'
# Use Active Model has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use Active Storage variant
# gem 'image_processing', '~> 1.2'

# Reduces boot times through caching; required in config/boot.rb
gem 'bootsnap', '1.4.6', require: false

group :development, :test do
  # Use sqlite3 as the database for Active Record
  gem 'sqlite3', '1.4.2'
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug',  '11.1.3',  platforms: [:mri, :mingw, :x64_mingw]
end

group :development do
  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
  gem 'web-console',           '4.0.2'
  gem 'listen',                '3.2.1'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring',                '2.1.0'
  gem 'spring-watcher-listen', '2.0.1'
end

group :test do
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara',                 '3.32.2'
  gem 'selenium-webdriver',       '3.142.7'
  # Easy installation and use of web drivers to run system tests with browsers
  gem 'webdrivers'                '4.3.0'
  gem 'rails-controller-testing', '1.0.4'
  gem 'minitest',                 '5.11.3'
  gem 'minitest-reporters',       '1.3.8'
  gem 'guard',                    '2.16.2'
  gem 'guard-minitest',           '2.4.6'
end

group :production do
  gem 'pg', '1.2.3'
end
# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data'

これはrails tutorialのものと同じです。