When I try to install purchased plugin on a 2nd test site,

When I try to install purchased plugin on a 2nd test site, it said it was not registered for one click. So I went and changed the settings so that this site was enabled (and disabled the original site). However, the message persists and the install option is still unavailable. Is this supposed to work? What am I missing? I have tried reloading browser, clearing cache, different browser.