QU-16 No Audio from Quicktime, YouTube etc.

Hello,
I have audio working fine when streaming from ProTools into my QU-16, and although I’ve previously had audio playback from Quicktime, YouTube etc via ST-1 (17-18) for some reason it has stopped working with this OSX playback.
I’ve confirmed all the settings are correct in the Audio/Midi Setup box, and do get the ‘white noise’ signal when I check the setup there.

Any suggestions as to why this is so and how to get it working again are appreciated.

why double post?