Your purchase is good for one licensed url for one year.  If you received the message ‘Serial key usage exceeded the allowed limit’, it means you are trying to license more urls than your license provides.

That said, you can transfer your license as long as it is valid (within the year’s time).

So if you receive this message ‘Serial key usage exceeded the allowed limit’ and

• You are trying to move a site to production from a staging site or
• You have recently added or removed SSL (your site changed from http to https or the other way around) or
• You have moved your site from or to a subdirectory

Go to your account page and delete the original licensed url.

Find the license you want to transfer, check the box, and click ‘Remove Licensed Site URLs’. Then you can validate the new url.

NOTE: Once a production url has been licensed, an additional site with ‘localhost’ or ‘staging’ in the url will be allowed. A staging site just can’t be the initial url to be licensed. So validate the url on the production site first, then on your staging site to maintain an active staging site while in production.