Hi, I have a few tips:
1. Dolby Digital. If the light is not on - check your TV settings thoroughly, my LG TV had two output settings! I set both on Auto, and voila, the DD light lit up on the 600.
2. On PCM, Surround mode does make quite a difference. On some DD movies it does, and others does not.
3. Ensure you have the latest Klipsch Connect app on Android/iOS, and you may be able to update the firmware. Also if it subsequently disconnects, remove the 600 as a device from the app, and re-add it.
Happy listening.