I just spent the best part of an hour messing around with Fail2Ban and having to connect to the problem host via a VPN.
I had been locked out of a host by the IP addresses of both my home and my offices – and it took me a while to realise what was going on!
It also turns out that different versions of fail2ban have different commands for removing bans – but this should work for all of them.
This will let you know the rule number that you need to remove:
iptables -nL -v --line-numbers | grep "your.ip.address"
And this will remove that rule from your IP tables rule set:
iptables -D fail2ban-ssh RULE_NUMBER