I've happily been using my old Olympus software to play my DSS files. However, my equally old footpedal is about to die, so I thought I'd check back to see if ExpressScribe was updated to fix the DSS problem. I just downloaded the latest version and tried to play a DSS file. Now there is a message box that pops up and says that "the file format is not supported" and it deletes the DSS file. I guess NCH has given up on ever trying to address this issue. It is very misleading to continue to purport on the ExpressScribe information page that DSS is a supported file type when it clearly is not. Maybe one of these days I'll get to use ExpressScribe if I receive something other than DSS files...
By the way, I also tried some of the other helpful hints added to this post, including the new codec file, but nothing worked. I'm not tech-savvy enough to try any of the more advanced solutions, so I give up.