WAV files must be in the correct format to work.
Assuming you have uploaded the WAV file to the music on hold directory, the command line conversion can be done as follows.
cd /var/lib/asterisk/moh
sox uploaded-file-name.wav -t raw -b 16 -r 8k -c 1 converted-file-name.wav
mv uploaded-file-name.wav uploaded-file-name.wav.orig
To preserve a higher definition sound file try:
sox uploaded-file-name.wav -t raw -b 16 -r 48k -c 1 converted-file-name.sln48
mv uploaded-file-name.wav uploaded-file-name.wav.orig
