Those MJ pouches are terrible if you don't know that the yeast, hops and instructions are in a pouch to the side of the malt extract.
What temperature do you think the
pouch reached when you heated it?
You 'may' have killed the yeast if the temperature was too high. If you have then you could buy some more from Crossmyloof (cheap and fast delivery) or go to Wilkos and buy some of their Gervin ale yeast.
Which yeast was supplied?
If it was MJ M44 then I have found it to be a really slow starter. Sometimes it can be up to 48 hours before I can see any activity. Just when I'm about to give up and pitch some more, a krausen starts to form.
Move the fv somewhere slightly warmer and give it 48 hours before starting to panic. In the meantime, buy some more yeast and keep it in the fridge as a back up