I am trying to upload my mp3 to a database. A message advises me to upload using mp3 format only. Why is this?

I converted a wav file to an mp3, but for some reason I can't upload to this site via a database. I have sent the same file to 2 people and both say that it uploads ok. It is very frustrating. I advise other people on how to do it and yet it fails on me. Can somebody out their help me please?