No Audio Activity in either Default Input or Main Mix Output


I have just installed Cubase Artist 8.5.0 (64 bit) on an iMac (OS X El Capitan) and am running it through a Focusrite Scarlett 6i6.

I can’t hear anything when trying to play back Instrument, MIDI or Audio tracks. There is no audio activity in either the default input or main mix output on the transport bar. I can see audio activity in the MIDI track, but not the Instrument (HALion Sonic SE) or Audio tracks.

I’ve updated to the latest version of Cubase Artist, as well as installed the latest ASIO drivers from Focusrite.

I’ve checked and double-checked, and the Scarlett 6i6 is selected and showing as Active under MIDI Port Setup, VST Quick Controls and VST Audio System. The correct Scarlett 6i6 inputs and outputs are also selected and showing as Active under VST Connections. The Scarlett 6i6 is currently set to buffer size 256.

The Scarlett 6i6 is set up as the default input / output for the iMac under System Preferences, and I’m having no problem hearing anything else through the 6i6 (iTunes, websites etc.).

I’m at a loss as to why Cubase isn’t registering any audio activity. Any help or guidance would be much appreciated!

Many thanks,