Why is there no Audio in my video play back when I know my camera supports audio?

This needs to be enabled in 2 places typically, log into your NVRs web interface and navigate to Configuration, Video/Audio and find the Video Type dop down menu, within this drop down, select both Video and Audio Streams. The second location to check can be found under Configuration, Storage, Schedule Configuration, on this screen, you will find a button for Advanced Parameter which will have a tick box to Enable Audio.