My Norton Anti-Virus has deactivated and unregistered a without me doing anything

I was browsing websites today and a message popped up asking me to purchase Norton 360 (even though I'm registered and have nearly 200 days left to re-register). 

 

I then clicked on my Norton 360 and it said I had to activate it. Rebooted my PC turned it back on to find the same issue. Logged into Norton Online, found that my product key had been deactivated.. Re-entered it again and it's back up and running.. 

 

Was I attacked by a Virus? Should I be concerned? Has anyone else had these issues?

Product is up-to-date with latest versions.