EZProxy won't work with the VPN (Pulse Secure). If you're using the Pulse Secure app to connect to the VPN; you'll have to log out before using EZProxy.
To turn off the Advanced Security feature in Xfinity, select the Account icon from the top-left corner of the Overview tab on the Xfinity app and then select xFi Advanced Security. From here, select Turn Off under xFi Advanced Security and follow the on-screen prompts.
Or, try accessing the link on your cell phone or mobile device using your data plan, not wifi (that is, don't use Xfinity wireless).