redmineの初期ページが表示できない

Question

前提・実現したいこと

CentOS7でRedmine4.1をインストールしました。
WEBサーバは起動しておりますが、ブラウザ上に以下文言が出ておりアクセスが出来ません。
どのようにすれば表示させることができるでしょうか。

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発生している問題・エラーメッセージ

/var/log/httpd/error_log内に以下エラーログを確認しました。

[ E 2020-11-26 03:24:23.1900 2099/Ta age/Cor/Con/CheckoutSession.cpp:285 ]: [Client 2-3] Cannot checkout session because a spawning error occurred. The identifier of the error is c9ec9b65. Please see earlier logs for details about the error.
App 2254 stdout:
App 2254 stdout:
[ E 2020-11-26 03:31:44.0900 2099/Tn age/Cor/App/Implementation.cpp:304 ]: Could not spawn process for application /var/lib/redmine: An error occurred while starting up the preloader.
  Error ID: 2bff5b8d
  Error details saved to: /tmp/passenger-error-LoCCCT.html
  Message from application: (<unknown>): mapping values are not allowed in this context at line 4 column 18 (Psych::SyntaxError)
  /usr/local/lib/ruby/2.5.0/psych.rb:402:in `parse'
  /usr/local/lib/ruby/2.5.0/psych.rb:402:in `parse_stream'
  /usr/local/lib/ruby/2.5.0/psych.rb:350:in `parse'
  /usr/local/lib/ruby/2.5.0/psych.rb:263:in `load'
  /var/lib/redmine/lib/redmine/configuration.rb:92:in `load_from_yaml'
  /var/lib/redmine/lib/redmine/configuration.rb:42:in `load'
  /var/lib/redmine/lib/redmine/configuration.rb:73:in `[]'
  /var/lib/redmine/lib/redmine/thumbnail.rb:25:in `<module:Thumbnail>'
  /var/lib/redmine/lib/redmine/thumbnail.rb:22:in `<module:Redmine>'
  /var/lib/redmine/lib/redmine/thumbnail.rb:21:in `<top (required)>'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:291:in `require'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:291:in `block in require'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:257:in `load_dependency'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:291:in `require'
  /var/lib/redmine/lib/redmine.rb:48:in `<top (required)>'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:291:in `require'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:291:in `block in require'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:257:in `load_dependency'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:291:in `require'
  /var/lib/redmine/config/initializers/30-redmine.rb:6:in `<top (required)>'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:285:in `load'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:285:in `block in load'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:257:in `load_dependency'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/dependencies.rb:285:in `load'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/engine.rb:663:in `block in load_config_initializer'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/activesupport-5.2.4.2/lib/active_support/notifications.rb:170:in `instrument'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/engine.rb:662:in `load_config_initializer'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/engine.rb:620:in `block (2 levels) in <class:Engine>'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/engine.rb:619:in `each'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/engine.rb:619:in `block in <class:Engine>'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/initializable.rb:32:in `instance_exec'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/initializable.rb:32:in `run'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/initializable.rb:61:in `block in run_initializers'
  /usr/local/lib/ruby/2.5.0/tsort.rb:228:in `block in tsort_each'
  /usr/local/lib/ruby/2.5.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
  /usr/local/lib/ruby/2.5.0/tsort.rb:422:in `block (2 levels) in each_strongly_connected_component_from'
  /usr/local/lib/ruby/2.5.0/tsort.rb:431:in `each_strongly_connected_component_from'
  /usr/local/lib/ruby/2.5.0/tsort.rb:421:in `block in each_strongly_connected_component_from'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/initializable.rb:50:in `each'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/initializable.rb:50:in `tsort_each_child'
  /usr/local/lib/ruby/2.5.0/tsort.rb:415:in `call'
  /usr/local/lib/ruby/2.5.0/tsort.rb:415:in `each_strongly_connected_component_from'
  /usr/local/lib/ruby/2.5.0/tsort.rb:349:in `block in each_strongly_connected_component'
  /usr/local/lib/ruby/2.5.0/tsort.rb:347:in `each'
  /usr/local/lib/ruby/2.5.0/tsort.rb:347:in `call'
  /usr/local/lib/ruby/2.5.0/tsort.rb:347:in `each_strongly_connected_component'
  /usr/local/lib/ruby/2.5.0/tsort.rb:226:in `tsort_each'
  /usr/local/lib/ruby/2.5.0/tsort.rb:205:in `tsort_each'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/initializable.rb:60:in `run_initializers'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/railties-5.2.4.2/lib/rails/application.rb:361:in `initialize!'
  /var/lib/redmine/config/environment.rb:14:in `<top (required)>'
  config.ru:3:in `require'
  config.ru:3:in `block in <main>'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/rack-2.2.3/lib/rack/builder.rb:125:in `instance_eval'
  /var/lib/redmine/vendor/bundle/ruby/2.5.0/gems/rack-2.2.3/lib/rack/builder.rb:125:in `initialize'
  config.ru:1:in `new'
  config.ru:1:in `<main>'
  /usr/local/lib/ruby/gems/2.5.0/gems/passenger-5.1.12/src/helper-scripts/rack-preloader.rb:110:in `eval'
  /usr/local/lib/ruby/gems/2.5.0/gems/passenger-5.1.12/src/helper-scripts/rack-preloader.rb:110:in `preload_app'
  /usr/local/lib/ruby/gems/2.5.0/gems/passenger-5.1.12/src/helper-scripts/rack-preloader.rb:156:in `<module:App>'
  /usr/local/lib/ruby/gems/2.5.0/gems/passenger-5.1.12/src/helper-scripts/rack-preloader.rb:30:in `<module:PhusionPassenger>'
  /usr/local/lib/ruby/gems/2.5.0/gems/passenger-5.1.12/src/helper-scripts/rack-preloader.rb:29:in `<main>'

試したこと

以下のサイトの丸コピです。
Proxy環境ぐらいの違いしかありません。
http://ishibashi.blog.jp/archives/4168469.html

補足情報（FW/ツールのバージョンなど）

Firewalld disable