Hi, I can help answer your question.
Sometimes the updates can cause this issue.
The only way to resolve the problem is to verify your product. To obtain a new product key for your Office program , call 1-800-936-5700 and speak to a Microsoft customer service representative. You will be able to verify your software by Product ID using the registry and get a replacement CD and license key.
I am in Australia the phone number you gave is for the USA
The activation wizard should give you a number for your region.