Client 12 loads character list from website instead of the server.
So your website needs to support it.
You can install latest version of Znote AAC:
Developement repository for the Znote AAC project. A website portal to represent and manage your Open Tibia server. - Znote/ZnoteAAC
github.com
and in config.php configure
$config['gameserver']
to match the data in config.lua (serverName, port, ip etc).
Then character list will be loaded, and you can connect to the game.