The update on your Samsung may have disabled/changed some settings.
I hope the following helps.
TV's need HDMI-CEC enabled on both soundbar and TV. Different makes call it by other names. Samsung call it Anynet+
Press the Home button your TV remote, and then navigate to and select Settings > General. Select External Device Manager, and then select Anynet+ (HDMI-CEC) to turn it on. Next, connect an external device using an HDMI cable, and then turn on the device - it will automatically connect to the TV.
partial success in that the Soundbar sound is again present for the vast majority of time. There is an odd instance several times each evening for the sound to disappear entirely. This lasts for up to 45 secs or so at a time before it resolves itself.
I had wondered if I connected with optical cable rather than HDMI there would be a different result but have not as yet attempted that.