You can only motivate someone so much. You need to try and understand why they are not motivated considering they have the skills. Best way is to ask directly

You can only motivate someone so much. You need to try and understand why they are not motivated considering they have the skills. Best way is to ask directly in a way that doesn't put them on the defensive. If the situation is same after multiple feedbacks, you need to fire them. Working with an unmotivated low output person makes you miserable. It doesn't matter how skilled they are.