When a new end user purchases a Plesk domain hosting plan, OBAS creates a new customer account and an FTP user account for Plesk. The password of the Plesk customer account differs from the password entered by the end user in online store during new OBAS account creation.
This is correct OBAS functionality.
When a new customer is created from OBAS store, the password is set for that account only. The OBAS customer password and different subscriptions passwords should be different. One OBAS customer can have many different subscriptions and each of those subscriptions would have a password of its own. Such behavior increases security.