It would have been nice if the guy who was emailing me from support had been aware of this problem instead of suggesting that it was a difficult level and I should just keep trying to complete it when it was impossible to do so.
After having a totally unhelpful support chat where he suggested that level 6628 was just a difficult level and sometimes it just takes longer to complete and to keep trying!! I had told him that my colour bombs were only getting me approx 10,000 points so I would need 50 colour bombs in 25 moves to achieve 500.000 points…