Cannot restore purchase – Kindergarten Math - Games for Kids in Pr-K and Preschool Learning First Numbers, Addition, and Subtraction Review

I bought this app on my other phone. Now I want to use it on my iPad but it does not restore the purchase. Please advice.
Review by searswins on Kindergarten Math - Games for Kids in Pr-K and Preschool Learning First Numbers, Addition, and Subtraction.