I worked on the same issue minutes ago on a 3.1(5) System
- Text Pager 1 was activated for all voice calls (not only urgent)
- The notification schedule was set correctly
- SMTP connectivity was verified between Unity Exchange Server and the destination Mailbox.
- One Unity Subscriber's e-mail (text pager) notification worked, another one (configured exactly the same!) didn't.
Rebooting Unity solved my problem - hope yours too..
/David