Many digital sound desks have an inbuilt USB audio interface - letting you connect your computer to the desk directly. When these desks are connected, they usually provide 16 or more channels of inputs.
This is great for DAWs and other software with complex audio needs, but can require some extra setup to use in CaptionKit or other web-based apps.
Having trouble with an already connected desk?
Browsers like Safari and Chrome often only use the first 2 input channels from a chosen device - this means that when your mic or FOH mix lands on anything except channel 1/2, CaptionKit can't see it.
Option 1 - Use a software audio routing option
This is usually the easiest approach, especially if other programs already use the channel mapping you have set up. Apps like SoundPipe let select the 2 channels you need and push them into a new virtual audio input - perfect for CaptionKit, Zoom and other apps to use.
SoundPipe - $10 / Free trial
SoundPipe is a newer option that does the important job of channel routing and virtual device setup. It's also only $10 as a one-time purchase.
https://soundpipe.app
Loopback - $99 / Free trial
The original and most full-featured option for virtual audio routing on a Mac.
https://rogueamoeba.com/loopback
Option 2 - Remap channels in the USB output
Each desk usually has the ability to map inputs to each channel in the USB output.
The important mapping is to make sure channels 1/2 receive the speech signal - whether as a main L/R pair, or as just the microphone input.
Please refer to your sound desk manual or manufacturer instructions for more info on this mapping.