sudo fail2ban-client status

Inspect one jail:

sudo fail2ban-client status sshd

Unban an IP address from a specific jail:

sudo fail2ban-client set sshd unbanip 203.0.113.10

If you do not know which jail banned the address, check the fail2ban log:

sudo grep 203.0.113.10 /var/log/fail2ban.log