If you son had no employment income and no "tax payable", after entering his tuition tax slips (T2202as) on his return, he should have an available tuition amount to transfer. You will need to check your entries, and ensure that the tuition amounts are showing up in the student summary.

Did you know that along with a full review of your return when you're finished, TurboTax Live Assist & Review users can contact an expert for assistance while preparing the return? 

https://turbotax.community.intuit.ca/replies/3456106