One of the WHD features is the ability to push notifications to your mobile phone using the Apple Push Notifications Service. This service requires a certificate which expires today. If you want to continue using these notifications you need to install the new certificate availalbe from your customer portal.
Click on License Management -> ChooseDownload (under Web Help Desk license information) -> scroll toTools & Plugins and click Download button next to "Apple Push Notification (APN) Certificate".