Did you enter your Activation Code before you started your returns? This TurboTax Canada FAQ tells you how to use your TurboTax Online Activation Code: In TurboTax Online, how do I use a prepayment code? 

Alternatively, if you didn’t use you code and instead started a return, when you get to the payment screen, you can put your activation code in the “Coupon Code” box and click “Apply Code” to use it.