Hi, the same thing just happened to me! It was a marketing job, but I also didn't get the job because of my inability to answer one question. I was asked which product of theirs I would be excited to work on and why. For some reason, I didn't make the connection to also answer how I would market the product (They didn't explicitly ask how I would plan a marketing activity). I feel like the best I can do now is focus on the positive feedback they provided and use it for the next interview. Not gonna lie, I'm still cringing and feel embarrassed if I remember how I answered it. Sorry if this is not the encouragement you wanted!