"My dear husband and I didn't have a single secret."
Translation:Mon cher mari et moi n'avions aucun secret.
In this case, it is most likely that you have something different from Duo's answer, something you did not notice. That is why people always copy their answers and paste them in the forum so that others can help to find the errors.
Quite often, people can find the errors by themselves after pasting their answers here.