Guys,
In Joomla system messages are displayed in the system message container. If you don't have this added to your template messages won't show up.
To check if it's present view the source code of your page in your browser and look for this code: <div id="system-message-container"></div>.
In case you don't see this you need to add this code. Either manually in your index.php or by enabling a setting in your template.
In case one of you is on Wordpress, please post your question here: https://wordpress.org/support/plugin/acymailing/