Pro Tools won't launch while Source-Connect/Live is open
Version 3.5 and up, macOS and Pro Tools
If Pro Tools or Source-Connect/Source-Live launches while the other application is selected to use Avid hardware, it will fail to launch.
Read below or More Info Here with Step by Step guide.
All macOS audio applications will try to use the System Audio preferences on first launch. If your System Audio preferences are set to Avid hardware, when you first launch Source-Connect you must either change the Source-Connect settings to built-in audio or another device (Pro) or change your System Audio preferences default hardware to built-in audio or another device (Pro and Standard).
If there is no built-in audio driver available for example on a trash can mac, you can use our free Source-Nexus I/O audio driver.