In order to make notifications work, you have to define a Cron job on your server. Follow these steps on Linux installations:
Execute the command “crontab -e” as root, to edit the crontab file
Place the following line inside your crontab file
*/5 * * * * /usr/bin/php /full_path_to_axs2lms/www/cron.php http://axs2lms.example.com
where /usr/bin/php is the path to the php executable on the server and the path for cron.php must be defined not from the DocumentRoot folder of installation but as the full path from the logical drive.
Make sure you specify an additional argument with the full url of your installation, for example, http://axs2lms.example.com or https://axs2lms.example.com.
The corresponding process on Windows servers is to create a Scheduled task that runs php.exe file appended by arguments /full_path_to_axs2lms/www/cron.php and http://axs2lms.example.com.
In case Schedule task can not run php.exe file you can create a batch file to call the executable with the arguments and modify the scheduled task to run the batch file.
Note: This is a necessary step for notifications into AXS2LMS. Without setting up a cron job emails generated from events are not delivered to their recipients and you see them always into Mail Queue tab.