A spore from a mushroom which germinates starts with the formation of primary mycelium. This mycelium is also called "monokaryotic" mycelium. Monokaryotic mycelium on its own cannot form mushrooms.
The monokaryotic mycelium must be placed in contact with another compatible monokaryotic mycelium. Secondary mycelium will then start to form. The secondary mycelium is called "dikaryotic" mycelium. Only dikaryotic mycelium can form mushrooms. The chance that only monokaryotic mycelium will grow in your substrate is generally too low.