"My luxury car, my husband broke it!"
Translation:Ma voiture de luxe, mon mari l'a cassée !
I typed "Ma voiture de luxe, mon mari l'a cassé" and it was accepted. It is one of the few times I have selected "my answer should not be accepted" when reporting.
This lesson seems to focus mainly on the use of the correct endings for the past participles. In particular, for verbs which require avoir as the auxiliary in the compound past tense, when the direct object precedes the verb the participle must agree with it in gender and number.
In my case, cassé was not a "typo". It was a mistake, a careless error, or an omission.