What do you mean by ‘pair’ with your LG TV? What connection method have you chosen to use with your TV? 

Most modern LG TV’s work connected over HDMI-2 ARC/eARC connection - if that’s what you are using, you just enable Simplink (CEC) and Auto-Power-Sync in the TV settings and set the sound-out to the HDMI-ARC port (with either pass-through (recommended) or Auto setting enabled) and if available set eARC to ‘ON’.

That normally works, but most Techs would likely know these things, so I’m surprised one of them was unable to sort it, unless there is a hardware fault?

Make sure the HDMI cable between the products is the one supplied by Sonos or at least has 1.4+ HEAC support.

Really appreciate your reply Ken - tried all you have suggested via the Sonas help line - to no avail! Spent over 90 minutes with him while he ran diagnostics- unplugged cords etc - still no response 

Going to try the sound bar on my Son’s TV just to see if it will working - process of elimination - the fault May b my LG tv, but that’s only a couple of years old - I’ve had the sound bar for 6 months???

Try this:

Disconnect everything from the TV including the Arc and unplug the TV and Arc from power for a couple of minutes. Then plug everything back in but keep everything disconnected. Enable Simplink on your TV, then run TV Setup in the Sonos app under the Arc’s settings. When the app instructs you to, connect the Arc to the TV’s HDMI ARC port using the Sonos-supplied HDMI cable. When the Arc has been successfully connected, connect any other device to the TV.