Your stacktrace clearly states that your db with name third doesn't have proper table person. But you shouldn't create this table manually (if you already had - please remove all tables from your db)
Connection seems fine but you should take a look at dbCreate value in your application.yml.
dbCreate - Whether to auto-generate the database from the domain model
- one of 'create-drop', 'create', 'update' or 'validate'
If you are using just simple command
grails run-app to start server, then you should check out the value in the environments: development block.
Paste your application.yml content (without db credentials) if you need a personalized solution.