Originally Posted by JulianCBrown:
“Sorry if I misunderstood you but it looked to me as though you were criticising me for trying to get help from more than one place!
I am sure that this should be simple to resolve but I have spent hours fiddling and got nowhere!”
The smiley face

at the end of the sentence should have given the game away that I was attempting humour, not criticising you.
In my experience, things like SRS get turned off and greyed out when they are not compatible with another setting within the TV. That other setting might be that you have selected a preset sound mode, or it could be as simple as you viewing material that is not stereo (unlikely, but possible). Hence my suggestion that you should look for some kind of custom sound mode.
I will carry on looking around for you, but please try to retrace your steps - as you wrote elsewhere, it was working to start with.