This is almost certainly one of 2 things, Selection and/or Routing.
You must ensure your route all of your tracks to a Master Bus (which YOU have to insert). If you use other busses to group like instruments together, these too must go to the Master Buss
If you mute your Master bus you should hear silence. If not investigate and rectify.
Selection. Either select ALL (ctrl + a) or select NONE (ctrl + shift + a). I prefer the latter.
Select File> Export.
Under Source Category choose Main Outs
you said you wanted a wav so select Stereo (Channel Format), 44100 (Sample Rate), 16 (Bit Depth), None (Dithering)
Tick all the other boxes.
Hit Export and choose a location for the wav.
If necessary, sweep in the timeline to select the exact length you want exported.
That's it, takes much longer to type it than do it.