It seems that unity returns no sound when triggering the playaudiofile() function, even after locating the correct file path to the audio asset within Unity’s asset folder. Been troubleshooting it for a bit and can’t seem to understand why FMOD is having issues.
That message indicates that no Sound was passed to the programmer sound during the callback. It’s likely that the Core API Sound object you’re creating in the callback is invalid in some way, or that it isn’t being assigned to the parameterPtr argument of the callback correctly. I would recommend observing the result returned by your calls to the FMOD API to see whether anything specific is going wrong.
If you are unable to track down the issue, feel free to upload your code (or a stripped down version of it) where you can reproduce the issue here so that I can take a look at it.