Passenger doesn't seem to be running (Capistrano/Rails/Nginx/Ubuntu)
This issue was fixed by adding restart.txt in my_app_name/current/tmp:
*It's done in the server:
*touch my_app_name/current/tmp/restart.txt
And add:
set :passenger_restart_with_touch, true in deploy.rb
UPDATE
In the newest version of capistrano, this is taken care of by gem 'capistrano-passenger' and adding adding require 'capistrano/passenger' in your capfile