What I've tested:
mp3 on my mounted "User" drive, U:/ Waveform works
mp3 on my mounted "Media" drive, M:/ Does not work
So I tried matching permissions, full control, owner, re-mounting a new network drive, network share, different letters, putting it in the root of the drive, still does not work.
I find this odd, and I know it's low-priority and i don't know if anyone else has this issue. But it's such a cool, useful plugin. If you want to pursue it I can dump logs.