I use PowerPoint to convert mine. Open a new slide, drag the recording over and save it as a MPEG4. I have uploaded several into my assessment and have never had a problem.

The most recent thing I have says “For best performance in PowerDMS, we recommend converting audio files to MP4 (.mp4) with h.264 codec.” You can Google how to do this if you want. I have the free download of VLC (which my agency actually approved for me to use) and this is the instructions for how easy it is to convert: 

1. Open VLC Media Player
2. Go to the Convert window
3. Under Settings, go to the Profile dropdown menu
4. Select Video - H.264 + MP3 (MP4)
5. Choose the location to save the converted video

Hope this helps!