I've already installed the needed tools, and followed several tutorials trying to make passenger respond.
I can access static files in public folder (public/500.html or 422.hml). Yesterday I entered through a vhost, and found some passenger errors. But some time later the hosting restarted the service, and since then I have not been able to access the rails app again.
These are some of the links I used to configure the server. I've also read that could be a permission issue; I've checked that, but I'm not sure it's fine.
Answer was that passenger gave me 403 because i had to set environment variable "RackEnv" on apache configuration to "development" (on my case).