Can't register License Key for Internet Security 2015

I was tempted by an offer on Ebay for a 3user x 3year Subscription for Internet Security 2015
It installed fine and seems to be working ok and updating but I noticed firstly the expiry date is for 26th February 2018 and not  5th May when I installed and when I try to register the License Key I keep being told it is a non valid License even though when I installed it the software itself has green ticked the License Key and says it's valid. The supplier tells me that the 3 months is how these promotional deals work and that the 3 months will be added at the end of the term but cannot explain why it won't register. He sent me another License key today and I am still getting non valid. Any ideas please.

No need for a response, I have decided that I am too unsure about this product and have uninstalled it and requested a refund. Thank you.

No need for a response, I have decided that I am too unsure about this product and have uninstalled it and requested a refund. Thank you.