You can register Rey theme through several ways. You will however need the purchase code before you start. How to get a purchase code?
Right after you activate Rey theme the first time, you should be redirected to a setup wizard. You can find the registration form into the first step.
If you’re not already registered, in the Dashboard page, you should see the registration form in the first box.
If you want to deregister, access Rey theme – Dashboard and in the first box, you should see the “DEREGISTER PURCHASE CODE” button.
This error can happen when the SSL certificate is not properly set into the site. First step to check this, is to access Settings in the backend and look at the Site Address and Site URL and check if they contain “https” protocol.
Unfortunately even though you’re using the key on your localhost, the key cannot be simultaneously active in multiple locations, so you will need to deregister from localhost first, and then register onto the live location.
Please know that almost all functionalities are enabled regardless if registered or not. The only limited/blocked functionalities are: getting update notifications, importing templates or premade sites. These are basically related to the cloud (where that data is stored and downloaded from) so it’s mandatory to be registered to keep our cloud service expenses low.
Yes it can. But please make sure to read this article too https://support.reytheme.com/kb/updating-on-multisite-installations/ .