There are a few issues we work on on touchscreen devices including iPad:
-when you join the interpreter of the Moderator console you may see the audio meter [Green, yellow, red] changing but no audio. In that case cycle the limiter: turn it off with the toggle button and then turn it on;
-iOS does not allow direct control of device volume. That is why the volume slider will not work. You will have to adjust the volume with the device buttons;
-depending on your bandwidth, video may not show on touchscreen devices.