Device selection is hardcoded
My mac has Loopback Audio app installed and as such your iOS device may not be device 3 in the list of AVdevices. This is currently hardcoded in line 46 (viewcontroller.swift) but can be of course be edited and rebuilt from source, devices are listed in output for debugging purposes such as this.
Possible Fix.
- Switch Devices via keyboard short cut (preferred)
- Check and use only iOS device