Rear Speakers Not Working

[JazzyJ]

To save a trip to my not so local Honda dealership for hopefully an in warranty repair, I'd appreciate any advise as to a simple cure to the following. On putting on the DAB this afternoon I noticed the rear speakers not working in my 2017 EX Jazz. If I faded everything to the rear, nothing! This was true of all sources (DAB. Bluetooth, FM,AM) and also after a 'default reset' of the audio settings. All was working fine prior to today. All help gratefully received!