The Lifetime Learning Credit is not a refundable credit. It reduces the tax you owe. And...the Lifetime Learning Credit is a credit of up to $2000.
"Not a refundable credit" means that the Lifetime Learning Credit cannot make your refund more than the tax you had withheld during the year. If, without the Lifetime Learning Credit, your refund was already equal to all the tax that was withheld, there's nothing more to be refunded. Adding the Lifetime Learning credit (or any nonrefundable credit) cannot make your refund any higher.