If you receive this error message when launching a Logic Pro X session, be sure to try the following:
1) Launch Logic Pro X and open the "Plugin Manager" found under preferences.
2) Type in "Slate" in the search bar on the top right. Click on the Virtual Mix Rack and then hit "reset and rescan selection".
3) A white box will appear and run some script. Once the process is complete, you should see the message "successfully validated...Done" at the bottom of the window. Click "done" and open Virtual Mix Rack from your plugins list. If you receive a different message please copy and send it to support.