Hey, welcome to the forum!
My suspicion about why you aren't hearing anything from the center channel when you watch TV is that the receiver simply isn't sending any signal to it. A lot of TV shows are in stereo, so your receiver will only play the sound through the front left and front right speakers by default - unless you tell it to do otherwise. Try this: set the receiver to play in a type of surround sound and check if you hear anything from the center channel. I recommend that you try Dolby Pro-Logic as the surround sound choice.