Visma Software Development Engineer interview questions

I had an initial interview for 15 mins. The next step was an assessment, which was creating a mobile application. This took me a week and more than 40 hours of work. After sending it, I received no feedback for more than 3 weeks (although I asked for it several times ). Then they send an email, that I was rejected with absolutely no information about why. I think it was not that fair after spending that much time for the task.