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