to list blocked IP's

iptables -L

To unblock an ip:

• (pre 8.8) fail2ban-client get ssh actionunban 10.xx.15x.12x
  (post 8.8) fail2ban-client set ssh unbanip 10.xx.15x.12x

where ssh is the jail name and 10.xx.15x.12x is the ip that has been banned.

the find the jail name just run

fail2ban-client status.

it should give a list of jail name.

fail2ban log2 to general meassages in /var/log/messages