I agree with Huckster's advice, it is very difficult to get a private car Insurer to accept no claims bonus from a Motor Trade Policy. As he has advised the first port of call is normally the Motor Trade Insurer, alternatively I assume you bought the policy through a broker, it would be worth also speaking to them as they will normally pull some favours in to get an Insurer to accept the no claims bonus.
Once you have completed a year on a private car policy your no claims bonus will then be a proper private car no claims bonus so should be accepted by the entire market