Having implicitly followed the instructions to re-order the channels at the end of the process TV switched off and restarted. Thereafter the sound bar no longer worked either on the HDMI ARC output or by using the optical connection.
After hours (literally) of trying to find the fault I found in the on board help menu that the TV had reset itself to basic and the sync to the sound bar and the Amazon Firestick had been lost. I reinstated the sync and all is well. So be warned when using the Channel Editor - or, of course, it could just be me!
