Some mp3 links you find on the internet may be temporary links (for instance it needs you to look at an advertisement before you can listen/download) and that's probably why your link may not work. A more steady method is to use
puush, which is a file sharing program that acts like imagur/4 shared/tinyurl all in one. Once you download the application, you can right click files such as mp3s and thus you have an mp3 link uploaded.