Just had another look at your recipe.
Cant see anything wrong with it at all.
You could add more yeast.(but i don't think you need to)
What will help is decanting from one demijohn to another a few times with maximum splashing and shaking.
This will dissolve some oxygen in the must allowing the yeast to grow.
I used to use an aquarium air pump for this purpose.
I say used to,Guess what happened to that .!! Gnash Gnash