Have you cleared cache? If you are using 6.3.9.1v of the theme and 2.3.9.1v of the Core plugin, but still face the problem with the activation, provide us with temporary wp-admin and FTP access, we will check the situation more deeply and help.
Create an account via Dashboard (Users > Add new) with administrator role http://prntscr.com/s3rc9m > provide us with username and password via the Private Content area http://prntscr.com/s5mao7 You can use any email for it. Delete the account once all questions will be solved. If you do not know how to create FTP contact with your hosting provider, they will help you.
