The .ds2 file format is a relatively new file format from Olympus. Only recent versions of DocShuttle Transcriptionist properly support this new file format. The first thing to do is to check to make sure that you have the latest version of DocShuttle Transcriptionist. To do this, click "Help | Check for Updates" from the DocShuttle menu.
If you have already downloaded some .ds2 files and are unable to play them, you may need to check to see if they have been renamed to .dss. If so, you will need to rename them back. In order to do this, open Windows Explorer and go the the installation folder (usually "C:\Program Files\Bytescribe\DocShuttle Client"). Then you will need to open the "type" folder into which the files were downloaded. There you will need to rename the files back from .dss to .ds2. Then refresh your DocShuttle window.