Try unplugging it for 15 to 30 minutes and try again. Mine did this last year and unplugging it got it working again. I had to reconfigure the settings again.
It sounds like a settings issue. Either on the receiver or TV or both. Check that they can pass Dolby signals. It probably won't work on PCM. Some receivers have the option for different sound on various settings. For example the one for TV could be switched off or on a different connection socket than the one you use. For example it might be on optical, or RF, or HDMI.
Make certain that any Blu-Ray player connected is putting out the right signals. Sometimes they can have the option to "mix" signals for certain TV's. This however will kill the signals needed for Atmos.
If there is no power at all, such as no lights at all. Then it has probably had an internal fuse failure, or something has gone in the power supply of the unit.
Power on the Harmon Kardon by pressing and holding the power button until it beeps.
then, press and hold the Bluetooth button (on H.K. Speaker) until it beeps.
Make the Samsung UN46EH5300 Bluetooth to be VISIBLE.
The H.K. will emit an audible when successfully paired.
Try setting up speakers through your TV. (I suppose your Tv is wifi in to tv) Tap menu on tv remote. Go to network. Tap wifi, then follow TV's direction.
it could just be a result from the streaming service itself buffering on your network so if the audio and video are not in sync while streaming try rebooting the streaming service and disconnecting and reconnecting the network. If its the TV itself that may have the problem then its an issue with the image processing and a quick fix to that is to set your TV into game mode.
