I have replied your email ticket as well. As you said i was thinking the same. This problem might be for others as well.
Your key was currently activated in localhost/wordpress/. I think you first setup this in your local server and then move it online. But might have forget to de-activate/re-activate the key for live site. So the key didn’t matched the domain and says invalid and the update was denied.
For now i have remove that entry and the key is free to use it in live site. Please activate the key now in your live url and the update should go fine.
For future, you can login to http://www.masonrylayout.com/your-account/ and can manage it from there.
Please let us confirm this. The license key will be valid for a year from the date of purchased. If the plugin says invalid you can check the license key from Your Account section to confirm. If the license key is active and still you are getting invalid then there is some issue. Please do let us know and we will fix as soon as possible.
For expired key, the plugin will mention expired in license key page.