as per my opinion the software is carsh...you should reinstall it...and also clear the cache
Try reinstalling the application.
I solved the issue by just adding extra DNS servers.
For my case, I just checked OpenDNS in that link http://192.168.0.11/admin/settings.php?tab=dns
By the way, http://192.168.0.11 is the addess of the PI, so change it by the address of your PI.
Good luck