Valcom 2901 A door buzzer not working with HT 503


I am having issues getting my Valcom 2901 A answering system to work with an HT 503 ATA. I did make sure that PSTN was set on and Line 1 was off when testing the system. I also tried connecting the Valcom line out to an analog phone and tested the doorbell but nothing came through.
Am I missing something?