"Ma soeur ne t'a pas vue aujourd'hui" was not accepted. I'm guessing it was because of "vue" (the extra 'e') but it said "aujourd'hui" was the wrong word.
It was a dictation exercise but the homophone "vue" cannot be recognized as correct.
Sometimes, when there is more than one error, the system focusses on one and ignores the other(s).
I put 'vue' as well, as an experiment, and it was , as stated above, marked wrong. But why is it not acceptable, if the person to whom you are speaking is a woman?