Unfortunately it is not so uncommon to apply to jobs and never hear back from the employer. However, I have never encountered a company that makes you do a non trivial programming task and then fails to even answer your emails or even acknowledge receipt of your application and completely ignores you. Even sent a follow up email and nobody ever responded. I think the job posting was inactive but they never bothered to take it down and no one is even reading the applications, because your effort and time is meaningless to this company.