Welcome to the Cake Decorators Q&A

I covered chocolate cake with chocolate ganache,put in the fridge to set,and then covered with roll out icing,left in cool place, by next day the icing was melting from inside and actually sliding of the cake not sure what I did wrong:(?

Hello Yvetta73

You haven’t really done anything wrong. You’re experiencing a moisture from within the cake problem. Have a peek at a similar question/answer posted by another member here:

Fondant sliding off choc ganache and air bubbles

Allow cake to come to room temp or until the dew on the ganache has dispersed before icing. If you still experience wet icing, sitting the cake near a fan will help the icing to dry.