Cepstral, no sound when using swift command

Hello.

Before I purchased a license from Cepstral I had the demo version of the 4.0 voices (allison-8hz). It was working perfect except for the nagging voice.
I decided to purchase the license since I was satisfied with the performance; however, once I finished installing the 5.0 voices and registered the license, the Swift command no longer generates any sound. It does not make a difference if I use it in a phpagi script or in the dial plan, they both produce the same results: no sound. In the script, it does not even pause, you see the command being executed on the cli however it just skips right over it.

If I use the -o argument to convert a text file it works. Currently I have a function in my script that does this whenever I need to use Swift however there is a slight delay and it 'stutters' a tiny bit when playing back the file. I never had any of these issues with the demo version though.

Does anyone know what can be wrong?

Thanks!