What does it mean that the licence is bound to one domain?

It means one licence works on one website address at a time: the domain where you first activate it. After that, the same key only runs campaigns on that domain.

• The domain is your site address without https://, for example mynews.com. The plugin reads it from your WordPress site address.
• If someone tries the key on another site, activation fails with License is bound to a different domain. This protects your credits from being used elsewhere.
• A staging copy, a local copy or a different address of the same site counts as another domain.
• Your Dashboard shows the bound domain on the licence card, plus a history of domain changes with date, action, from and to.

To use the licence on a new site, click Reset Domain in your Dashboard and activate it there. To run several sites at the same time, each site needs its own licence; contact support to get more licences on your account.