On a Mac, you can reset activation by clicking Shift+A on the Purity interface to "De-Authorize" before attempting a fresh activation.
Unlike some modern plugins that use a simple cloud login, Purity uses a two-step offline/online hybrid method: purity vst serial number and authorization code
If you have purchased a legitimate license from Sonic Cat (the current distributors of LUXONIX technology), follow these steps: On a Mac, you can reset activation by