Don’t panic! This is completely normal. The first thing to make sure is that you have folded your cheese cloth over enough times to make sure that the mesh is fine enough to trap the curds (this won’t apply if your kit came with a 30cm² square butter muslin, you shouldn’t need to fold at all).
If this hasn’t solved your problem then you should add another half teaspoon of citric acid (dissolved in 50ml water) into your milk and reheat until it’s just about to boil. Continue doing this until the curds are left in the cheese cloth, but do be cautious because you don’t want to end up with overly sour milk.