im also getting the 422 error message when creating a new project. i just deleted the connection between github and sonarqube and recreated but still getting the 422 error. i gave sonarqube full access to my org and all repos 
Failed to search repositories for searchQuery 'org:mygithubid fork:true': 422. {"message":"Validation Failed","errors":[{"message":"The listed users and repositories cannot be searched either because the resources do not exist or you do not have permission to view them.","resource":"Search","field":"q","code":"invalid"}],"documentation_url":"https://docs.github.com/v3/search/","status":"422"}