Pretty sure you have to change the config depending on the distro you are using. Not sure if your FC is the same as my centos 5, but my log I'm using for checking ftp connections is /var/log/secure, but you currently have it to check /var/log/proftp/proftpd.log
I'm not saying what you have is wrong but check your logs to make sure that matches.
The other thing to check is the proftp filter in your /etc/fail2ban directory. The actual filter may not be correct to match the log entry.