Some browsers may have a problem playing some MP3 audio files that you upload to your Digital Press Kit or Media Center page. When this happens, it is usually when Firefox or Internet Explorer are being used to view your website. Both of these browsers require Adobe Flash in order to play MP3 files.
The most likely cause is the way the audio file was encoded. All MP3 files you upload should be saved with the following encodings:
Encoding: Constant Bitrate Encoded
Sample Rate: 22,050Hz or 44,100Hz
Additionally, if the audio file size is over or near 10 Megabytes, you may also want to use a lower bit-rate such as 128 kbps.
Online Audio Converter
If you have a non-standard MP3 file or some other type of audio file, trying using Online-Convert.com to convert it to an MP3 file (it's free). Set Audio Bit-Rate to 128kbps and Sampling Rate to 44100 Hz.