You are required to report any T slips issued to you when filing your return. If your T4A contained scholarship/bursary income and you were a full-time student, the amounts would have been exempt from tax, but still entered into your return.
When you entered your T4A information into TurboTax last year, there were options to enter your box 105 amounts into one of 4 different spots - each one with a description of why it would be chosen (screenshot below). If you were a full-time student or qualifying part-time student and entered the amount in one of those boxes, the income would have been exempt.
To make the correction to your return, you'll just need to file an adjustment. Here's how: https://turbotax.community.intuit.ca/replies/2647992