To start using ParkPlusMC you first have to register your license
/parkplus license register sbd <license>
Once you've registered your license you can now link it to your account
/parkplus license link <license>
Always make sure to stop your server before changing any files or versions of the plugin. Reloading will break stuff, and configurations are saved on disable. Meaning that all the .yml files of ParkPlus you've edited before the server went off are rewriten.