Symptoms
Notification about service provisioning are configured as described in KB #117294. But customers are not notified anyway.
Cause
The Notification Template has field "To Address" set to @@Cust_User_Email@ while such placeholder cannot be used for Notification Templates of type "Subscription notification".
Resolution
Use placeholders @@Cust_Account_AdminContact_Email@ or @@Cust_Account_BillingContact_Email@ instead.