railsでactive_supportが読み込めない

Question

rails newした時に以下のようなエラーが出てしまいます。どなたか教えていただけると幸いです。

$ rails new test_prj                                                                          
Traceback (most recent call last):
	10: from /usr/local/bin/rails:23:in `<main>'
	 9: from /usr/local/bin/rails:23:in `load'
	 8: from /Library/Ruby/Gems/2.6.0/gems/railties-6.0.2.1/exe/rails:10:in `<top (required)>'
	 7: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	 6: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	 5: from /Library/Ruby/Gems/2.6.0/gems/railties-6.0.2.1/lib/rails/cli.rb:12:in `<top (required)>'
	 4: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	 3: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	 2: from /Library/Ruby/Gems/2.6.0/gems/railties-6.0.2.1/lib/rails/command.rb:3:in `<top (required)>'
	 1: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- active_support (LoadError)
	11: from /usr/local/bin/rails:23:in `<main>'
	10: from /usr/local/bin/rails:23:in `load'
	 9: from /Library/Ruby/Gems/2.6.0/gems/railties-6.0.2.1/exe/rails:10:in `<top (required)>'
	 8: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	 7: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	 6: from /Library/Ruby/Gems/2.6.0/gems/railties-6.0.2.1/lib/rails/cli.rb:12:in `<top (required)>'
	 5: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	 4: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
	 3: from /Library/Ruby/Gems/2.6.0/gems/railties-6.0.2.1/lib/rails/command.rb:3:in `<top (required)>'
	 2: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:34:in `require'
	 1: from /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:130:in `rescue in require'
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:130:in `require': cannot load such file -- active_support (LoadError)

試したこと

• sudo gem install activesupport

　→インストールはできるが、エラーは変わらない