The issue may be with your server. We host the updates on our own server and some hosts might block the download. We are working on getting to the bottom of the issue, but in the mean time, you can update your plugin manually by doing the following:
1. Download the zip file from: http://access.accessally.com/popupally-pro/installation/
2. Delete PopupAlly Pro from the plugins list in the WordPress dashboard
3. Upload the zip file and install the latest PopupAlly Pro
Please contact us if you have any questions!