I suggest you email them like everyone has said.
I see you don't have a medal on your avatar, which means you didn't purchase the license here on this site. So I assume you brought it via steam, in which case you don't need a license as steam handles this for you.
Or three you have obtained an illegal version and the update nulled it.
There are 2 places to purchase construct2. Here on this site and on steam. Which place did you purchase it?
If you purchased it here. Then email scirra and they will sort you out quickly. Or you can download a new license file from the store under your downloads.
If you purchased it from steam, then best contact steam.
If you got your copy anywhere else, then I'm sorry buying pirated software isn't smart.
But I hope you brought it here or steam. Because it takes a single email to sort it out.