Years subscription lost after downloading update

Hi, I have a Norton Internet 2010 2 years subscription and am nearly one year into it.  Last week I kept getting pop up messages telling me to download a free update but the message also said my subscription will continue as normal afterwards.  I downloaded the update and now my subscription is saying I have a 30 day free trial and then I need to pay to subscribe fully.  Any idea how I can get my previous subscription back which still has a year left to run?   I cannot find the box which has the key number on it at home, can I find it on my computer anywhere?

 

Any help gratefully received as I do not want to purchase a new subscription when I have already paid for two years worth.

 

Many thanks