Hello Roderick,
That error message means that the audio driver has lost communication with the audio interface.
First, as a test to try to determine whether the problem is due to macOS having insufficient free RAM (which often does make macOS' audio stop working properly), please try:
- Reboot the computer.
- Load St. Anne's (which doesn't use much memory).
- Leave the computer untouched for a few hours.
- Unload St. Anne's.
If you then still get the same error then I think the problem will be that macOS has put the audio driver (or one of its components, or some other USB device) to sleep, resulting in the connection between the driver and the interface being lost. In that case, please:
- Disable macOS 'App Nap' globally: https://osxdaily.com/2014/05/13/disable ... -mac-os-x/ .
- Make sure that any available power-saving options are disabled in macOS' system preferences. In particular, don't allow the Mac to go to sleep, and disable any other options relating to things being put to sleep.