thanks for your response.
The email addresses are listed under this section but this line or the firmware guide makes me think any operational admin should receive the notification:
Can firmware upgrade scheduling be completely disabled?
No, firmware upgrade scheduling cannot be disabled. However, firmware upgrades can always be canceled, and organization admins are, by default, notified via 'Scheduled maintenance' emails when firmware upgrades are scheduled.
Anyway, the configuration has not changed and we used to get the notifications, so I believe something else is wrong here.