I have fixed my with help from Sony support.

Sony suggested that I should remove AC power from the TV for 30 seconds and disconnect all HDMI inputs apart from the link between base/TV via ARC HDMI 2 and then power up. This instantly activated the sound system immediately. Then it was just a matter of connecting 1 x input at a time until the problem re-occurs, in my instance it was an android TV box I had connected that had CEC enabled this caused a communications failure between the TV and soundbase.

Good luck.