Well if you have an ip banned then you should deleted as this
iptables -L --line-numbers
And then run this where chain-name you should replace it with what name you have there for example fail2ban-ssh
iptables -D chain-name 2
Short update on this
You can run also
fail2ban-client status
and after this
With Fail2Ban before v0.8.8:
fail2ban-client get YOURJAILNAMEHERE actionunban IPADDRESSHERE
With Fail2Ban v0.8.8 and later:
fail2ban-client set YOURJAILNAMEHERE unbanip IPADDRESSHERE