As explained so many times on the forum ( and on the manuals too ), you should never ask questions about activations issues on the forum because, my next question would have been "what's your key ?" or "what's your order number ?", and we cannot obviously discuss this in public.
Contact support by email, using the address listed in your purchase receipt or the "Contact Us" page of the site, with all the required information about your key and your order and, possibly, a screenshot of your error.