Why can't I activate after system restore?

Explanation:

It might be possible that system restore has deleted the product's license file and damaged the activation module, causing the activation status to become "trial." If you have forgotten to deactivate before system restore, please refer to the further reading section at the end of this article.

Solution: 

1. Follow the instruction in this article to uninstall
2. Install the software (if the installer is nowhere to be found, go to our official website download page)
3. Use the same serial number to activate

Further Reading
I've reached the activation limit, what should I do?
How do I clean activation record online?