TV has stopped muting via Alexa

[DavidR2]

I have a QE85Q60TAUXXU TV.
I’ve operated the TV with an Alexa Echo device successfully for over a year. I would turn the tv off, change channel and mute and unmute, without a problem, all by my voice. But all of a sudden Alexa has stopped muting, unmuting or changing sound volume!!! But I can still change channel and turn the TV off with my voice via Alexa. 
I’m turned the power off to the TV for a hour a couple of times, reset my broadband and unpaired the TV then paired it again on my Alexa App to kickstart it back to fully operating, but it’s not working.
How can I get Alexa to mute, unmute and change volume again?

[RetroRampage]

I have no idea. I never operated Samsung tvs via alexas.

[BigRedBoat]

I'm having the same problem. Mine worked fine until about a week ago and now Alexa will only turn the TV off and change channels. No volume or mute and it will not turn the TV on. I've deleted and reloaded the apps and devices, changed names of devices: I can't figure it out. Worked fine, then nothing, very frustrating!