The send issue notifications in batch feature requires a recurring task for issue notification be created first, otherwise issue notifications will not be sent.

Recommended best practice is to have the user who handles study configuration and has the necessary privileges setup the recurring task for issue notification before any send in batch issues are created. Once this task is created, it applies to all users on the URL who select the send in batch option, and issue notifications will be sent according to the schedule set in the task.

Checkout the "Setup Batch Issue Notifications Using Tasks" tutorial for more details!