DDJ GRV 6 not recognised by iMac - Flashing Lights of Doom!!

Hi Folks,

I have a new DDJ GRV6 and I have connected it to my 2015 iMac which has the lasts OS adn latest Rekordbox.

I only have flashing red lights on the trims 1, 2, 3 & 4 and flashing yellow in and out buttons.

It's connected using a mains adapter to the power port and i've tried several USB A to C cables but no luck. I've also tried the cable it came with with an adapter on it.

It works fine plugged into a Windows PC.

When I look in system and the USB section it does not show up.

Any pointers greatly received :-)