If you're getting a red screen with "We're sorry but something went wrong" message, then that's rails complaining and not apache (the web server) or something else.
This might be a stupid question, but did you do "rake db:migrate"?
If you look in the application's 'logs' directory, you should see a file called "production.log". From the command line of your webserver do "tail -f production.log" and then use your browser to make the error happen. You can see in real time what is going on with your application, and if you scroll through that log you should see the complaint.
My guess is that you don't have the tables set up correctly in the database, which db:migrate should fix.