Trying to cover a cereal treat model with MMF and it is falling off. I coated the cereal treats with buttercream and then covered it in fondant. Now the fondant is falling off almost as if it is melting.

try undercoating with:

thick buttercream,

royal icing,

melted chocolate,

modeling chocolate, or

chocolate ganache

use a thick layer of fondant, or two layers of fondant, (perhaps strengthened with Tylose)

several videos are online for instructions. good luck with your project.