Lindsey, Food Editor replied
Hello,
40 minutes without a setting marmalade isn’t right.
It could be that….
You used too much water or not enough oranges or not enough sugar.
You didn’t extract enough pectin from the muslin bag.
The heat was too low so you didn’t fast boil the marmalade.
Take a look at the cookery school to see if it helps.
Best wishes
Lindsey