Face Time Isn't Ringing on MacBook Pro

I have a new MacBook Pro. My son called me via FaceTime several times but it did not ring, make a sound or give me any notification. I tried going to settings in FaceTime to poke around - but nothing. However, when I called my son from my FaceTime on my MacBook Pro he received a notification that I was calling. Please note I don't have an iPhone. My son does have an iPhone if it makes any difference.

Thank you.