@Monica.loberto We are having issues with T3 box 21. For the error on the T3 slip not balancing box 52+53 to equal box 21A, trying to enter the sum of 52+53 into box 53 (deleting 52) should fix the problem.
We are aware of this issue, and our development team is working on a resolution. We appreciate your patience.
Thank you for choosing TurboTax.