Just done a firmware update in offline mode using latest updater, once completed I unplugged the USB and carried out a global reset 9 & 10 etc.
Powered the unit up whilst disconnected from PC, nothing - no audio from guitar into direct monitors. Tried various inputs, even reconnected the USB and still no audio from the PC. HX Edit will still control the unit, but no audio.
I've text the seller a couple of times, he replied last night saying he would get in touch today as he was at work all day yesterday.
Find it difficult to believe the unit has developed the fault in the 20 minutes I used it at home. Although the seller may not have known, as he told me he didnt use the USB when I asked when I viewed the unit. To be fair he had a Focusrite on his desk etc. Noticed the unit was on firmware 2.5 when I briefly tested it at his home, so when I got it home and setup, the first thing I did was upgrade to 3.5 then tried to use it, but I've had no use of the unit due to the no sound issue etc.
Will wait till he gets in touch today. I think it's fair to say the unit is faulty at this stage.