Perhaps you are looking in the wrong place for those log files? I don't see anything wrong with what you posted, and it says to write the logs into the /logs folder. So do you have such a folder? Does your server have permission to write in it and create files in it?
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com
subject: Using FileAppender - Unable to log to a file