Best Music Remix App so far but problem with that – Music Speed Changer Review

I enjoyed using this app, but one reason is wrong. I tried to pick a song from Dropbox and it’s not working. It’s kept saying “Error while loading Audio Files”. It’s there’s something wrong? Did I forgot something? I found a song from YouTube and Musi (one of the music app). But it’s not working. Plz help me get this work. If this is a bug or glitch the happened to me a lot (unable to play a Dropbox song), plz get em out by the next update.
Review by Ian Drezek on Music Speed Changer.