Changes to various linux and module updates, manual and automated, that were made during December/January, cause the PHP-IMAP module to become un-installed/deactivated/turned off.
The effect of this is that arpReach is unable to send broadcast messages while in many cases autoresponder messages and test messages will continue to send.
Broadcast messages will not send OR the first batch will send but further batches will not continue
The 'Scheduled task' bar within arpReach will display 'still running' and will not return to it's default state of 'currently idle'
Ensure that the PHP-IMAP module is installed, activated and configured to run with both PHP and CLI
Ensure that the path to your cron task is correct.
Your hosting company should be able to assist you with resolving this.