You can unban a player here: https://exaroton.com/players/banned-players
Or you can unban the player with the command /pardon [name] in the console when your server is online. Open the console here: https://exaroton.com/console/
If you've banned the player IP you can unban the player here: https://exaroton.com/players/banned-ips
Or you can unban the player with the command "/pardon-ip [ip]" in the console when your server is online. To get the IP address, list all IP bans with the command "/banlist ips".