I applied online and was contacted by the CEO, with whom I had a very nice and informative conversation. On the same day, I was also scheduled to interview with the Co-Founder and the Head of Product. All interviews went well and were conducted on a professional level. However, after these interviews, all my follow-up messages via LinkedIn and email went unanswered. I am left with the impression that the CEO's conduct has been unprofessional, particularly in terms of communication and feedback.