Indeed Software Engineering - New Grad interview questions

After meeting a recruiter, I was contacted to have a phone screen. It was a 30 minute technical interview on HackerRank's CodePair platform, which was easy to use. I had the flexibility to choose language. The question was very simple and related to string reversal, and I got it right, leaving time for me to ask the interviewer questions about the company. The interviewer was friendly, but I was completely puzzled by the reject I got from them a week after, considering there was not much room for error in the phone screen.