Consider the following scenario:
You deploy a dual tone multi-frequency (DTMF) based Interactive Voice Response (IVR) application in a Microsoft Skype for Business Server 2015 environment.
The application is developed by using Unified Communications Managed API.
The application joins a conference.
A user connects to the application, and then the user starts pressing DTMF digits.
In this scenario, the DTMF tone is missing.
This issue occurs because the Audio Video Multipoint Conferencing Unit (AVMCU) does not process the DTMF tone when the DTMF packets that carry the end of tone flag are dropped in the network.
To fix this issue, install the following updates: