Can you help? My son attended university full-time with a modest income. He has a refund coming but Turbotax will not all him to transfer his income to his parent. Why?

The tuition transfer is a non-refundable tax credit that you can use to reduce the tax that you paid or may have to pay. It can’t be used to generate or increase a refund. So, if you don’t have any taxes payable, you will not get the credit.