HT503 Voice Alarming but no DTMF response?

I’m currently using Ignition v7.9.7 with the voice alarm module and a Grandstream HT503 gateway. I’m able to receive calls from the gateway just fine, and I hear “This is an Ignition alarm notification. Please press any key to continue.” I followed all of the steps in the HT503 guide ( and support has confirmed I have the correct settings.

However, no matter what keys I press or for how long I hold the buttons, I cannot seem to get past the initial prompt. I’ve been advised by Ignition support to contact Grandstream support, and Grandstream has advised me to install Wireshark and start watching packet traffic. I’m not too familiar with Wireshark, but it did not seem like the HT503 device was reading any of the key presses, which would explain why Ignition isn’t seeing anything in the CallManager logs.

Has anybody else had a similar experience? Is there a missing parameter for Grandstream HT503 setup?

In SIP connections, DTMF signalling is often intercepted and delivered out of band, instead of the actual tones. I don’t remember all of the combinations, but you need to have that set to match everywhere along the chain. The component with the least configurability will have to be accommodated.