Rails: I don't get any error messages in my loge file only 500 page

I have a rails 3 app which is running with puma. When open localhost:3000 there is always the 500 page shown. I've tried to set binding.pry and log messages across the files (e.g. ApplicationController), but it seems they are never reached. I changed the root path to a controller that does not exist, still no log messages. So it seems like the route is never reached as well. I ve looked into the rails log, puma log, rack log but nothing is shown. Any idea how to get appropriate error messages? Please help, I am so frustrated, looking for the erros for days.