Intech Creative Services Senior Software Developer interview questions

I'm a mobile developer, but my resume got selected for full stack mobile app developer. They gave me an assignment to complete with Java Spring Boot and create an flutter application (Design was provided). I completed it in 24 hours, while they gave me 48 hours for it. After submission the reviewed the code and asked for 2-3 changes, and did it instantly. After that, they have arranged a client interview (DP World). I joined the interview and answered most of the questions. Questions was put on Java and Flutter, but I got stuck on a coding question. They also asked me to gothorugh the assignment code. The next day, I got the email that I'm shortlisted, and the recruiter will call me. I waited for 2 days, then I called the recruiter, and they suddenly said that your interview feedback was negative and we are not continuing with your profile.