To use the mastering options do I need to re-upload a song from my file library?

Unfortunately at this time the only way to use the mastering options on a file that has been saved to your library is to re-download the original version, and then re-upload it to use the mastering options.

This is something we are aiming to fix in the very near future however, so stay tuned to our product updates and emails to be alerted when it has been changed!