Unable to play on Kristal Tape transport.

Hi,
I have imported a wav file into the waver. I can see the audio on the track. I have been able to play and record on other devices.
When I press play on the transport, the light turns green and nothing else happens. The transport position does not change and the position bar does not change. The wind/rewind buttons move the position bar and the position indicator. The Locate start/end buttons also work. It does not matter where I position the position bar, play does not work. This is not a sound issue, but seems to be something in the tape transport software.
I have tried a re-boot to no avail. I could re-install Kristal I guess.
Any suggestions would be most welcome.
Thanks.
Ciarriadh