Expired MS-Office Home and Student Edition

11 months ago, I bought a premium version of MS-Office Home and Student Edition. Just today, I was surprised to see that it already expired. I searched on the FAQ page to contact Microsoft’s customer service support, but no one is available to chat or talk with. I have the installation disk with me and a valid product key. But every time I open MS-Office, it is expired and cannot be used. What is causing the problem? How can I resolve this? Please help me.
