I’m not in the UK but I assume the Sky Q is the same as a cable box in the US. The most common solution to a situation like this is to:

1. Remove all devices from the TV
2. Connect the Sky Q box to an HDMI port other than the eARC
3. Setup the Arc or Beam2 to the eARC port on your TV
4. Connect the Hue Sync box and sources (if any) according to it’s manual

Let us know if that resolves the issue

This could be a CEC (Consumer Electronic Control) spat -- they are very common. Many manufacturers have private names for CEC. You could experiment with turning OFF the SKY or HUE’s CEC, if that is possible. Another approach is to defeat the CEC connection to BEAM. 

Hi,

I have now tried all scenarios.

This scenario works fine.

hdmi Sky q to synch box, then synch box to hdmi on tv (non arc)

optical from Sky q converted to hdmi on Beam.

as soon as I plug the beam into the hdmi Arc the synch box stops working, the beam sound works in both scenarios.

cec cannot be turned off with the beam plugged into the tv as it automatically turns on.

so generally ok but cannot get Atmos on the beam using the optical connection 

I guess Philips will blame Sonos and Sonos will blame Phillips.

I can see that this has been raised a number of times but still no fix 

You might have some success inserting the CEC defeater. (If you are the DIY type, mechanically defeat pin 13 in the HDMI cable, but don’t attempt this with a cable you like or is buried in the wall)

Thanks for that, I have purchased a CEC defeater pass through plug from Amazon and this seems to have cured the problem. Now the Hue Synch is working with the Beam through HDMI.

I have exactly the same problem. Please tell me what cable to buy and how are the connections, above all it is worth losing the Atmos

I would assume they are referring to this CEC-Less adapter to disable CEC communication:

https://www.amazon.com/Lindy-HDMI-Adapter-Female-41232/dp/B00DL48KVI

Ok thanks, but the question is what device do I plug it into? that adapter, to the sync box or sonos beam 2. And really what is lost with that adapter?

Is it still needed then?

I thought Philips fixed the issue with a firmware update on their sync box. Users just connect their Sonos HT direct to the TV’s HDMI-ARC/eARC port …and the sync box (and connected devices) are attached to one of the TV’s HDMI Ports - If one of the connected devices is perhaps attempting to steal the CEC focus away from the Sonos HT product and you cannot switch off CEC on that device, then you could use the CEC-Less adapter in that case.

Some Hue Sync users have reported A/V dropouts too when using Dolby Vision on the newer Apple TV 4K - many users appear to say the best way to fix that is to set aside the HDMI cable that comes with the Sync box and use a high-speed hdmi cable in its place. You should find more information about that on YouTube and other sites online. HTH.