Used tretinoin after a year and no peeling. Why not?

I agree that a patient does not have to have peeling in order for Tretinoin to be effective.  Tretinoin comes in different strengths (0.025%, 0.05%, and 0.1%) and I'm not certain of the strength that you are currently using.  I recommend that you consult with a board-certified dermatologist in your area to be evaluated.  If you are applying a milder strength, the board-certified dermatologist after evaluation may suggest a stronger strength.  I hope this helps.

You don't have to peel for Retin-A to be effective. It's just a common side effect of it. "This
answer has been solicited without seeing this patient and cannot be
held as true medical advice, but only opinion. Seek in-person treatment
with a trained medical professional for appropriate care."