There might be a problem with the file format of the .wav file. As this has to have exactly the following settings:

PCM, 8.000 Hz, 16 Bit, Mono

It is possible to check it with the Sound - Audiorecorder from MS that is integrated in the Message Control configuration too.

Other possibility if I donīt hear the .wav file beeing played is that, there is a connection to the Runtime with a remote Desktop Client of Microsoft. In our test was this effect only with remote Desktop of Microsoft. With other remote Desktop applications was it not reproducible.