If you are unable to access the event page on your device and are receiving a default message from your firewall, you will need to contact your network administrator. It is likely you will need to whitelist the event URL in order for your firewall to grant access.
If contacting your network administrator is not an option, please try to access the event on another device. A personal device will solve the problem in almost every instance.
In the event you are still unable to access the event on a personal device, your router firewall may be blocking your access. In this instance you can try to access the event via a different network or even over mobile data.