Make sure that your firewall settings whitelist the following domains for MasteryConnect:
*.masteryconnect.com
*.gradecam.com
-.ws.pusherapp.com
*.learnosity.com-.
*.socrative.com
*.pubnub.com
The asterisk (“ *. ”) indicates that this domain needs to be wildcarded to unblock all subdomains.
Be sure to whitelist all @masteryconnect.com emails.
Also, make sure to unblock the following ports: 80 and 443.
If you are using Online PD, there are some additional URLs that require whitelisting.