Sound on Samsung TV not working

I recently bought a cable TV off FB marketplace and I was told it was in good condition. I've just finished setting it up and hooking it up to my DVD player, but the sound isn't working and the remote control works selectively. I can turn it on, change the HDMI, but whenever I try turning the volume up, a message pops up saying "this is not available." That message pops up for a lot of buttons I press. I also cannot press play when I load a disc into the player. I'm not sure if this is an issue with the remote, the TV, or my DVD player. Any help would be appreciated, thanks.