I can’t seem to get sound from HDMI / ARC from TV to sound bar when watching Netflix /internet content from TV anymore

Sky box is connected with optical cable and sound plays through sound bar ok . 

I can also get sound and internet content through the DVD player connected to soundbar through HDMI. 

I used to be able to get sound from ARC with some intermittent drop out. Now, nothing. 

I’ve changed HDMI cables and they are high speed 4K compliant. 

Is it HDMI port failure?

Is it software?

Is it settings?