Meta Software Developer interview questions

Got a referral and received an email few days later about moving forward. However, the process took around a month because my recruiter left his job. The transition was not smooth and I followed up many times until someone helped me. It was a month and half since I got the first email when I interviewed. The experience wasn't great. The problem I got was really easy and I solved it pretty quickly with no bug. My solution was optimal and the interviewer told me it works and he is happy with it, but I still got rejected after a few days