iptables -L-output looks normal, for a fail2ban-setup that haven't detected anything bad going on.
Verify the following:
- is fail2ban running? Run
ps aux | grep fail2ban, you should see a
/var/log/fail2ban.log have any content? (If this file does not exist, check
/etc/fail2ban/fail2ban.conf for logtarget.)
If you still can't figure it out, it would be cool if you added the Linux-distribution, and version of fail2ban in use. You should also provide what kind of attack you want to defend yourself against. I have assumed ssh brute-force above.