"Upgrade Now" button on "Free Protection Upgrade" window does not respond

Hello, I have Norton AntiVirus (Mac) v. 12.9 installed on my mid-2014 Macbook Pro (Mac OS 10.11.3). During the past few days, a window began popping up, stating that a Free Upgrade to NAV is available. I'm attaching a pic of the window.

The problem is that the button does not work. When I click on it, nothing happens. Has anyone else had this problem?

Thanks.