The plugin's license keys are linked to domains. One license key is valid for one domain. You can link and unlink license keys from domain. For example, it can be useful, if you would like to transfer a Pro license key from your staging site to your live site. If you would like to transfer a Free key between domains, it can be done in the same way. Here are the steps you should follow:
1. Unlink your license key from the current domain
The first step is to unlink the key from your current domain. To do this, go to your account at cusrev.com. After you login to the dashboard, go to License Keys page. In the list of license keys, find the key and you would like to transfer and click on the vertical ellipsis button as shown on the screenshot below. Next, click on Unlink from domain button.
2. Register your license key for the new domain
Now, your key is not linked to any domain. So, it is possible to register the license key for your new domain. To do this, copy the license key (make sure you do not copy extra spaces in front or after the license key) and go into the admin area of your WordPress site. There, you should navigate to the License Key tab in the settings of the plugin (Reviews > Settings > License Key). Enter your license key into the License Key field and press Save button. Your license key has now been successfully transferred to the new domain.