Your character needs motivation to solve the problem. Why must your character confront this challenge? What is the outcome your character hopes for?
Sometimes this is obvious, sometimes not. For example, if your main character is a fox, and his challenge is to help some chickens get across the river, the reader needs to understand why the fox wouldn't just eat the chickens instead, since that's how a fox would naturally behave. Perhaps the chickens have promised the fox something in return for helping them? Or maybe the fox is afraid that the farmer will catch him if he eats the chickens.
Making your characters act against their nature can build great tension, but it has to be believable to your reader. Here are some ideas that might motivate your character.
Perhaps your character...
is bored with life on the farm
needs medicine to cure an illness
wants to protect the magic spell book
is tired of the rain
wants to be famous
feels like something is missing
Write down the motivation that your character has in order to overcome the challenge!