This probably means that the recording is not being uploaded correctly. In that case there should be an error in either the apache logs, or in the browser console. That would be good to see.
How about these questions:
i) Do very short recordings of just a few seconds work?
ii) If you turn on "show download button beside player" in the PoodLL filter settings, can you download the audio submission?
iii) If you can download it, how big is it? Does it play on your desktop?
iv) if there is a file but it doesn't play, can you post the file as an attachment here.