FaceTime does not ring when Mac sleeps

[bronzeye007]

Hello, I recently got my first Mac since 2013. Here's small problem, I forgot how to fix this problem that FaceTime does not ring when Mac sleeps. When Mac sleeps, FaceTime won't ring when someone called. For even I couldn't see the screen showing that too. Notification shows that it's already on. I have no clue how to fix it. Does it mean that I have to set display as off by either one to three hours unless there is another way to fix it that allows FaceTime to be ringing from Mac sleeps? I hope someone has great answer to help me with this issue. Many thanks and it's good to be back on Macrumors after awhile.