Hi Everyone

I have this set (XR75x9J and HT-SF150) and the soundbar wont play sound when connected with the HDMI cable in the ARC HDMI 3 port. 

There is a picture that says i have to change channel to hear sound, so i know it is connected. When i change to a channel, there is no sound. 

It plays fine with the optik cable and bluetooth.

I have a brand new HDMI 2.1 cable

Can anyone please help ? The store where i bought the TV and soundbar say that it should work.