Susan1945,
Try checking to make sure your receiver is receiving a 5.1 audio signal, and that the receiver is set to play a 5.1 audio signal. Without surround sound, the center channel will offer no audio.
If you continue to experience difficulty, try reaching out to the Best Buy Geek Squad Agents or the Samsung customer service center directly for live troubleshooting.
Thanks for your interest in Samsung products.
--Mr. S