Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
First of all, check the time and date setting - even and especially to the year, which should be 2015 for sure - on your computer. Make sure it is set to the right time zone, also, for your region, as well as the correct date in all paticulars, and the correct time (within 10 minutes at least) in your particular time zone.
This can be important for a variety of operations which involve secure transactions of a type that uses verifying software aspects known as 'certificates'. If the date and time (and especially, the year!) are set wrong, this can cause the sort of problem you report.
Then, with the date and time set, try to activate your copy of Sage software, once again.
Note down, if it fails again, what the full and exact text of the error message you get, is. Thanks.