Hello,
Please provide URL of your site, temporary wp-admin and FTP access.
wp-admin access: 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.
ftp access: If you do not know how to create FTP contact with your hosting provider, they will help you.
What is the path to reproduce the mentioned by you situation, so that the letter arrives (after registration or purchase or something else? – this is to know how to re-create it).
Regards