If you are not getting audio on your files, it is likely because the file's audio codec is:
- Not AAC format.
- Audio compressions is too high.
- File has more than 2 audio channels
- Audio is stereo L/R which is not supported
- Audio is missing from the source file
Keep in mind that playback on the web is different than that of the playback on your computer which supports a variety of formats and audio compressions that may not work in a browser.
You will want to re-export the file again with AAC selected. We have more info on encoding for third party players as well in related articles