Problem: Couldn't recognize CP2615 as output audio device in Mac OS when configured for 24-bit-only output.
Root cause: The failure to enumerate is due to the Mac OS not tolerating the Interface 3 Alt 1 zero-bandwidth descriptor that is sent by the CP2615 when configured for 24-bit-only operation. The presence of this zero-bandwidth descriptor is not prohibited by the USB standards and is tolerated by other operating systems (Windows, Linux, Android).
Workaround: The problem can be avoided by configuring the CP2615 Audio Out interface for 24/16 bit operation, instead of 24-bit-only. This just adds the 16-bit capability in addition to 24-bit, so there is no loss in the quality. 24-bit source material will still be sent over USB as 24 bits; the only difference is that 16-bit source material will get transmitted across USB as 16 bits, rather than being artificially padded to 24 bits as it would if the CP2615 was configured for 24-bit-only operation. (Padding 16-bit audio to 24-bit does not increase its actual resolution, it just wastes USB bandwidth.)