Unsound?

Exasperating lack of TV-soundbar communication.
Both worked perfectly until a few days ago. I have done nothing, changed no settings, added nothing new…in short, done sod all which would logically stop the Tv talking to the sound bar. The cables are fine, I bought a new one just in case. The sound bar works perfectly with other devices via Bluetooth.  The telly speakers are fine. I’ve downloaded a manual and all settings seem correct. Both devices are Sony, and have been in complete harmony until now.

ARGHHHH!

Ahem. Sorry. Anybody experienced this before and got any words of wisdom?