Sun disapear in the sky after starting the game

Hello everyone;
Actually i have a problem, when i start playing my game in the editor, the sun will disappear in the sky after seconds, i don’t know why this happen; is it normal or i did something mistake?
thanks for your attention!
here is the video:

Put a post process volume in the level and set

image

image

You can change the brightness if you want with the Exposure compensation slider.