Zaktualizuj wersję Ruby
rvm list known
rvm install ruby@latest
ruby -v
## If it still shows you ruby 2.0., run rvm use ruby-X.X.X --default.
Undefined
rvm list known
rvm install ruby@latest
ruby -v
## If it still shows you ruby 2.0., run rvm use ruby-X.X.X --default.sudo rvm get head
sudo rvm install ruby-2.7.4-railsexpress
rvm use --default ruby-2.7.4-railsexpress