You may also need to check your network’s firewall settings. In many schools, this problem blocks voice downloads. We use port 443 for downloading voices. This is the default HTTPS port used for securely browsing the Internet. Proloquo2Go also needs access to two servers: apps.assistiveware.com and download.assistiveware.com
If your internet connection is unreliable or you cannot change the firewall settings, you will need to try connecting to a different network.