my 06 octy has dual filament bulbs in both sides but only the drivers side comes on. an anker tow bar has been fitted with a 7 way bypass relay and some other boxes.

 

is it normal for only one fog to be on? is it a case of using vcds to enable both?

Yes and Yes!

Sadly as standard only the driver's side rear fog light is activated as standard ... Quite why I've no idea as its not saving Skoda any money doling it ... Yes someone with VCDS  should be able to activate it as long as they know what their doing as I'd one chap have an attempt at mine and it's still not working 

Yes, ever since someone "decided" that 2 rear fogs could be confused for brake lights!