ZSD Supervisor not receiving all appropriate emails

Since upgrading ZSD from version 23.4 to 24.4, a customer's ZSD Supervisor is not longer receiving all email message he used to receive. He used to received emails when new requests were created, when he made comments, or when his users made comments, when his requests were reassigned, etc., but now he gets nothing. The only email he does get is the 'Test email server setup' email. Nothing else has been changed in the environment with any association to the ZSD upgrade. the customer in question is the only Supervisor in the environment. Admins appear to be receiving all expected emails.