What are different domains?
Our single site plugin may only be used on one domain. If you switch your website from “www.example.com” to just “example.com” (or the other way around), that’s a different domain. So you’d need to deactivate on the initial domain first, before trying to activate on the new domain.
The same goes for domains switching from “http://www.example.com” to “https://www.example.com” (or the other way around).
So, if you make any changes to your domain, be sure to always deactivate your license on your initial domain first.
Further more, a single site plugin is also per WordPress installation. If you are running a development or staging site on your domain, that is considered a second website. For example, if you have “http://www.example.com” for your live site, and “http://staging.example.com” or even “http://example.com/staging” for your development site, then that is two sites.
In this instance, you would also have to deactivate your license before moving from the development site to the live website.