Zoom Rooms NDI - Not outputting telephone audio

Hi,

I am using Zoom Rooms NDI function to do live video production however we cannot seem to get the audio from a participant that dials in via audio (telephone). It works fine with participants who join the meeting from a device such as a laptop or computer but not when they dial-in from their phones. 

Please do not suggest that they use the Zoom app on their phone as this is not a viable solution for my workflow. They need to be able to call into the meeting and this audio be picked up via NDI. 

Does anyone have any suggestions?