Knowledgebase:
After Upgrading from ZBrush 2018 I Get an Error When Activating 2019
Posted by Matthew Yetter, Last modified by Matthew Yetter on 15 June 2019 08:06 AM
There are a few different errors that we've seen with activating ZBrush 2019 as part of an upgrade from 2018.  In every case, we've found that it has been because the user did not first deactivate ZBrush 2018 and reset the licensing system.

Please do the following:
  1. With ZBrush closed, browse to its folder and run the Pixologic Deactivation Manager
    • On Windows, the default location is C:\Program Files\Pixologic\ZBrush 2019
    • On Mac, the default location is Applications\ZBrush OSX 2019
  2. In that application, locate the ZBrush2018 activation.  Select it and click Deactivate.
  3. At the lower left corner of the application, click Reset.  Confirm when prompted.
  4. Close the Pixologic Deactivation Manager.
  5. Launch ZBrush 2019 and activate again.

This should resolve your issue.