I am hoping that someone who is smarter than me.....

can help me. My grandson and I rented a movie yesterday that we planned on watching on our bedroom TV, which has a VCR/DVD player hooked up to it. The movie came on alright, but there was no sound. The grandson messed around with the plugs, making sure everything was tight, we made sure the mute was not on, we tried the volume on both of the remotes, cable and TV..............nothing worked. We had played an old VCR movie tape about a month ago and the sound was fine. I know it's probably something really simple, but we just can't figure it out.