I posted this back in January but did not receive a solution so I'm posting it again and asking if anyone is having the same problem.
Here's what happens when I:
1. Open any song
2. Right click on any track except Drums
3. In the dropdown menu, click on Select Hi-Q MIDI Synth patch OR Select MIDI Synth or Audio Plugin
4. Select any instrument in the list box
5. Click the Play button. I get a Message box that shows the file path as C:\bb\DX Settings\(file name).tgs OR C:\bb\DX Settings\Amplitube\(file name).tgs
6. Click OK on the Message box
7. Get an error message that says there is no audio demo available for the file followed by the file path/name.
Please try this and let me know what happens for you. I'm using BIAB 2015 build 415. Thanks a bunch!