"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.
Why is the French sentence asking for a French translation? Was it a listening exercise? I don't understand.
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?