Can't generate Appflux config on Rails 2.7.1

[herunan]

rails generate appflux_ruby:install
/Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/actionpack-6.0.3.4/lib/action_dispatch/middleware/stack.rb:37:in `build': undefined method `new' for "AppfluxRuby::Rack::Middleware":String
Did you mean?  next (NoMethodError)
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/actionpack-6.0.3.4/lib/action_dispatch/middleware/stack.rb:136:in `block in build'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/actionpack-6.0.3.4/lib/action_dispatch/middleware/stack.rb:132:in `each'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/actionpack-6.0.3.4/lib/action_dispatch/middleware/stack.rb:132:in `inject'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/actionpack-6.0.3.4/lib/action_dispatch/middleware/stack.rb:132:in `build'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/railties-6.0.3.4/lib/rails/engine.rb:513:in `block in app'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/railties-6.0.3.4/lib/rails/engine.rb:509:in `synchronize'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/railties-6.0.3.4/lib/rails/engine.rb:509:in `app'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/railties-6.0.3.4/lib/rails/application/finisher.rb:97:in `block in <module:Finisher>'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/railties-6.0.3.4/lib/rails/initializable.rb:32:in `instance_exec'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/railties-6.0.3.4/lib/rails/initializable.rb:32:in `run'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/railties-6.0.3.4/lib/rails/initializable.rb:61:in `block in run_initializers'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/tsort.rb:228:in `block in tsort_each'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/tsort.rb:431:in `each_strongly_connected_component_from'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/tsort.rb:349:in `block in each_strongly_connected_component'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/tsort.rb:347:in `each'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/tsort.rb:347:in `call'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/tsort.rb:347:in `each_strongly_connected_component'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/tsort.rb:226:in `tsort_each'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/tsort.rb:205:in `tsort_each'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/railties-6.0.3.4/lib/rails/initializable.rb:60:in `run_initializers'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/railties-6.0.3.4/lib/rails/application.rb:363:in `initialize!'
	from /Users/herunan/code/herunan/MyNewApp/config/environment.rb:5:in `<main>'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/bootsnap-1.5.1/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/bootsnap-1.5.1/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/bootsnap-1.5.1/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/bootsnap-1.5.1/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/bootsnap-1.5.1/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/zeitwerk-2.4.1/lib/zeitwerk/kernel.rb:33:in `require'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/activesupport-6.0.3.4/lib/active_support/dependencies.rb:324:in `block in require'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/activesupport-6.0.3.4/lib/active_support/dependencies.rb:291:in `load_dependency'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/activesupport-6.0.3.4/lib/active_support/dependencies.rb:324:in `require'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/spring-2.1.1/lib/spring/application.rb:106:in `preload'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/spring-2.1.1/lib/spring/application.rb:157:in `serve'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/spring-2.1.1/lib/spring/application.rb:145:in `block in run'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/spring-2.1.1/lib/spring/application.rb:139:in `loop'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/spring-2.1.1/lib/spring/application.rb:139:in `run'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/spring-2.1.1/lib/spring/application/boot.rb:19:in `<top (required)>'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
	from /Users/herunan/.rbenv/versions/2.7.1/lib/ruby/2.7.0/rubygems/core_ext/kernel_require.rb:72:in `require'
	from -e:1:in `<main>'