rubyバージョンを変えたら、サーバーに表示出来なくなりました

本日昼、さくらVPSよりruby2.3.0からruby2.3.1に切り替えてとのエラーがありました。

もう少し最新版にと思い、ruby 2.4.1へ変更しました。

そうするとrails sやraiks dbが一切通らなくなり、WEBサーバーにもサイトがアップされなくなりました。

rails sを行なったところ、以下のようなエラーが発生します。

サポート頂けないでしょうか？

よろしくお願い致します。

$ rails s
=> Booting Puma
=> Rails 5.1.6.1 application starting in development 
=> Run `rails server -h` for more startup options
Exiting
/var/www/xn--vckvb6c8fw90p7kt9m0f.jp/public_html/crm/config/environment.rb:3:in `<top (required)>': undefined local variable or method `z' for main:Object (NameError)
	from config.ru:3:in `require_relative'
	from config.ru:3:in `block in <main>'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/rack-2.0.6/lib/rack/builder.rb:55:in `instance_eval'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/rack-2.0.6/lib/rack/builder.rb:55:in `initialize'
	from config.ru:in `new'
	from config.ru:in `<main>'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/rack-2.0.6/lib/rack/builder.rb:49:in `eval'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/rack-2.0.6/lib/rack/builder.rb:49:in `new_from_string'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/rack-2.0.6/lib/rack/builder.rb:40:in `parse_file'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/rack-2.0.6/lib/rack/server.rb:319:in `build_app_and_options_from_config'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/rack-2.0.6/lib/rack/server.rb:219:in `app'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/railties-5.1.6.1/lib/rails/commands/server/server_command.rb:24:in `app'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/rack-2.0.6/lib/rack/server.rb:354:in `wrapped_app'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/railties-5.1.6.1/lib/rails/commands/server/server_command.rb:80:in `log_to_stdout'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/railties-5.1.6.1/lib/rails/commands/server/server_command.rb:42:in `start'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/railties-5.1.6.1/lib/rails/commands/server/server_command.rb:135:in `block in perform'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/railties-5.1.6.1/lib/rails/commands/server/server_command.rb:130:in `tap'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/railties-5.1.6.1/lib/rails/commands/server/server_command.rb:130:in `perform'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/thor-0.20.3/lib/thor/command.rb:27:in `run'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/thor-0.20.3/lib/thor/invocation.rb:126:in `invoke_command'
	from /home/smart/.rvm/gems/ruby-2.4.1@global/gems/thor-0.20.3/lib/thor.rb:387:in `dispatch'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/railties-5.1.6.1/lib/rails/command/base.rb:63:in `perform'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/railties-5.1.6.1/lib/rails/command.rb:44:in `invoke'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/railties-5.1.6.1/lib/rails/commands.rb:16:in `<top (required)>'
	from /var/www/xn--vckvb6c8fw90p7kt9m0f.jp/public_html/crm/bin/rails:9:in `require'
	from /var/www/xn--vckvb6c8fw90p7kt9m0f.jp/public_html/crm/bin/rails:9:in `<top (required)>'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `load'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/client/rails.rb:28:in `call'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/client.rb:30:in `run'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/spring-2.0.2/bin/spring:49:in `<top (required)>'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load'
	from /home/smart/.rvm/gems/ruby-2.4.1/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `<top (required)>'
	from /var/www/xn--vckvb6c8fw90p7kt9m0f.jp/public_html/crm/bin/spring:15:in `require'
	from /var/www/xn--vckvb6c8fw90p7kt9m0f.jp/public_html/crm/bin/spring:15:in `<top (required)>'
	from bin/rails:3:in `load'
	from bin/rails:3:in `<main>'